From a944a271f2e27253a1e1ee9b812fa3dc1b8b0dde Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Wed, 17 Feb 2021 17:39:19 +0100
Subject: [PATCH 01/64] Update offsets.pyx

Fixes to year, quarter and month offsets.
---
 pandas/_libs/tslibs/offsets.pyx | 269 ++++++++++++++++++++------------
 1 file changed, 166 insertions(+), 103 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 2d4704ad3bda6..14dac644442a1 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1838,12 +1838,11 @@ cdef class YearOffset(SingleConstructorOffset):
     """
     DateOffset that just needs a month.
     """
+    
     _attributes = tuple(["n", "normalize", "month"])
 
-    # _default_month: int  # FIXME: python annotation here breaks things
-
     cdef readonly:
-        int month
+        int month, _default_month, _period_dtype_code
 
     def __init__(self, n=1, normalize=False, month=None):
         BaseOffset.__init__(self, n, normalize)
@@ -1853,6 +1852,8 @@ cdef class YearOffset(SingleConstructorOffset):
 
         if month < 1 or month > 12:
             raise ValueError("Month must go from 1 to 12")
+            
+        self._period_dtype_code = PeriodDtypeCode.A + self.month % 12
 
     cpdef __setstate__(self, state):
         self.month = state.pop("month")
@@ -1865,8 +1866,11 @@ cdef class YearOffset(SingleConstructorOffset):
         kwargs = {}
         if suffix:
             kwargs["month"] = MONTH_TO_CAL_NUM[suffix]
+        else:
+            if cls._default_month is not None:
+                kwargs["month"] = cls._default_month
         return cls(**kwargs)
-
+    
     @property
     def rule_code(self) -> str:
         month = MONTH_ALIASES[self.month]
@@ -1902,40 +1906,58 @@ cdef class YearOffset(SingleConstructorOffset):
         )
         return shifted
 
-
-cdef class BYearEnd(YearOffset):
+    
+cdef class YearBegin(YearOffset):
+    """
+    DateOffset increments between calendar year begin dates.
+    
+    Examples
+    --------
+    >>> from pandas.tseries.offsets import YearBegin
+    >>> ts = pd.Timestamp('2020-05-24 05:01:15')
+    >>> ts + YearBegin()
+    Timestamp('2021-01-01 05:01:15')
+    >>> ts + YearBegin(normalize = True)
+    Timestamp('2021-01-01 00:00:00')
+    >>> ts + YearBegin()._from_name('APR')
+    Timestamp('2021-04-01 05:01:15')
     """
-    DateOffset increments between the last business day of the year.
 
+    _outputName = "YearBegin"
+    _default_month = 1
+    _prefix = "AS"
+    _day_opt = "start"
+    
+
+cdef class YearEnd(YearOffset):
+    """
+    DateOffset increments between calendar year ends.
+    
     Examples
     --------
-    >>> from pandas.tseries.offset import BYearEnd
+    >>> from pandas.tseries.offsets import YearEnd
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts - BYearEnd()
-    Timestamp('2019-12-31 05:01:15')
-    >>> ts + BYearEnd()
+    >>> ts + YearEnd()
     Timestamp('2020-12-31 05:01:15')
-    >>> ts + BYearEnd(3)
-    Timestamp('2022-12-30 05:01:15')
-    >>> ts + BYearEnd(-3)
-    Timestamp('2017-12-29 05:01:15')
-    >>> ts + BYearEnd(month=11)
-    Timestamp('2020-11-30 05:01:15')
+    >>> ts + YearEnd(normalize = True)
+    Timestamp('2020-12-31 00:00:00')
+    >>> ts + YearEnd()._from_name('AUG')
+    Timestamp('2020-08-31 05:01:15')
     """
 
-    _outputName = "BusinessYearEnd"
+    _outputName = "YearEnd"
     _default_month = 12
-    _prefix = "BA"
-    _day_opt = "business_end"
-
-
+    _prefix = "A"
+    _day_opt = "end"
+    
+    
 cdef class BYearBegin(YearOffset):
     """
     DateOffset increments between the first business day of the year.
 
     Examples
     --------
-    >>> from pandas.tseries.offset import BYearBegin
+    >>> from pandas.tseries.offsets import BYearBegin
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
     >>> ts + BYearBegin()
     Timestamp('2021-01-01 05:01:15')
@@ -1951,36 +1973,47 @@ cdef class BYearBegin(YearOffset):
     _default_month = 1
     _prefix = "BAS"
     _day_opt = "business_start"
+    
 
-
-cdef class YearEnd(YearOffset):
-    """
-    DateOffset increments between calendar year ends.
+cdef class BYearEnd(YearOffset):
     """
+    DateOffset increments between the last business days of offset years.
+    Here, the year is a period of 12 consecutive calendar months
+    (January - December by default). The "month" parameter allows custom setting 
+    of the final month in a year (and correspondingly - the year start month). 
+    
+    Parameters
+    ----------
+    n : int, default 1
+        Number of years to offset.
+    normalize: bool, default False
+        If true, the time component of the resulting date-time is converted to 
+        00:00:00, i.e. midnight (the start, not the end of date-time).
+    month: int, default 12
+        The calendar month number (12 for December) of the ending month 
+        in a custom-defined year to be used as offset.
 
-    _default_month = 12
-    _prefix = "A"
-    _day_opt = "end"
-
-    cdef readonly:
-        int _period_dtype_code
-
-    def __init__(self, n=1, normalize=False, month=None):
-        # Because YearEnd can be the freq for a Period, define its
-        #  _period_dtype_code at construction for performance
-        YearOffset.__init__(self, n, normalize, month)
-        self._period_dtype_code = PeriodDtypeCode.A + self.month % 12
-
-
-cdef class YearBegin(YearOffset):
-    """
-    DateOffset increments between calendar year begin dates.
+    Examples
+    --------
+    >>> from pandas.tseries.offsets import BYearEnd
+    >>> ts = pd.Timestamp('2020-05-24 05:01:15')
+    >>> ts - BYearEnd()
+    Timestamp('2019-12-31 05:01:15')
+    >>> ts + BYearEnd()
+    Timestamp('2020-12-31 05:01:15')
+    >>> ts + BYearEnd(3)
+    Timestamp('2022-12-30 05:01:15')
+    >>> ts + BYearEnd(-3)
+    Timestamp('2017-12-29 05:01:15')
+    >>> ts + BYearEnd(month=11)
+    Timestamp('2020-11-30 05:01:15')
     """
 
-    _default_month = 1
-    _prefix = "AS"
-    _day_opt = "start"
-
+    _outputName = "BusinessYearEnd"
+    _default_month = 12
+    _prefix = "BA"
+    _day_opt = "business_end"
+    
 
 # ----------------------------------------------------------------------
 # Quarter-Based Offset Classes
@@ -1991,19 +2024,21 @@ cdef class QuarterOffset(SingleConstructorOffset):
     #       point.  Also apply_index, is_on_offset, rule_code if
     #       startingMonth vs month attr names are resolved
 
-    # FIXME: python annotations here breaks things
-    # _default_starting_month: int
-    # _from_name_starting_month: int
 
     cdef readonly:
-        int startingMonth
+        int startingMonth, _default_month, _period_dtype_code
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
         BaseOffset.__init__(self, n, normalize)
-
-        if startingMonth is None:
-            startingMonth = self._default_starting_month
-        self.startingMonth = startingMonth
+       
+        if startingMonth is not None:
+            if startingMonth < 1 or startingMonth > 12:
+                raise ValueError("Month must go from 1 to 12") 
+            self.startingMonth = startingMonth
+        else:
+            self.startingMonth = self._default_month
+        
+        self._period_dtype_code = PeriodDtypeCode.Q_DEC + self.startingMonth % 12
 
     cpdef __setstate__(self, state):
         self.startingMonth = state.pop("startingMonth")
@@ -2016,8 +2051,8 @@ cdef class QuarterOffset(SingleConstructorOffset):
         if suffix:
             kwargs["startingMonth"] = MONTH_TO_CAL_NUM[suffix]
         else:
-            if cls._from_name_starting_month is not None:
-                kwargs["startingMonth"] = cls._from_name_starting_month
+            if cls._default_month is not None:
+                kwargs["startingMonth"] = cls._default_month
         return cls(**kwargs)
 
     @property
@@ -2070,7 +2105,7 @@ cdef class BQuarterEnd(QuarterOffset):
 
     Examples
     --------
-    >>> from pandas.tseries.offset import BQuarterEnd
+    >>> from pandas.tseries.offsets import BQuarterEnd
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
     >>> ts + BQuarterEnd()
     Timestamp('2020-06-30 05:01:15')
@@ -2081,9 +2116,9 @@ cdef class BQuarterEnd(QuarterOffset):
     >>> ts + BQuarterEnd(startingMonth=2)
     Timestamp('2020-05-29 05:01:15')
     """
+    
     _output_name = "BusinessQuarterEnd"
-    _default_starting_month = 3
-    _from_name_starting_month = 12
+    _default_month = 3
     _prefix = "BQ"
     _day_opt = "business_end"
 
@@ -2098,20 +2133,20 @@ cdef class BQuarterBegin(QuarterOffset):
 
     Examples
     --------
-    >>> from pandas.tseries.offset import BQuarterBegin
+    >>> from pandas.tseries.offsets import BQuarterBegin
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
     >>> ts + BQuarterBegin()
-    Timestamp('2020-06-01 05:01:15')
+    Timestamp('2020-07-01 05:01:15')
     >>> ts + BQuarterBegin(2)
-    Timestamp('2020-09-01 05:01:15')
+    Timestamp('2020-10-01 05:01:15')
     >>> ts + BQuarterBegin(startingMonth=2)
     Timestamp('2020-08-03 05:01:15')
     >>> ts + BQuarterBegin(-1)
-    Timestamp('2020-03-02 05:01:15')
+    Timestamp('2020-04-01 05:01:15')
     """
+    
     _output_name = "BusinessQuarterBegin"
-    _default_starting_month = 3
-    _from_name_starting_month = 1
+    _default_month = 1
     _prefix = "BQS"
     _day_opt = "business_start"
 
@@ -2123,20 +2158,26 @@ cdef class QuarterEnd(QuarterOffset):
     startingMonth = 1 corresponds to dates like 1/31/2007, 4/30/2007, ...
     startingMonth = 2 corresponds to dates like 2/28/2007, 5/31/2007, ...
     startingMonth = 3 corresponds to dates like 3/31/2007, 6/30/2007, ...
+    
+    Examples
+    --------
+    >>> from pandas.tseries.offsets import QuarterEnd
+    >>> ts = pd.Timestamp('2020-05-24 05:01:15')
+    >>> ts + QuarterEnd(2)
+    Timestamp('2020-09-30 05:01:15')
+    >>> ts + QuarterEnd()._from_name('JUN')
+    Timestamp('2020-06-30 05:01:15')
+    >>> ts + QuarterEnd(1, normalize = True)
+    Timestamp('2020-06-30 00:00:00')
+    >>> ts + QuarterEnd(-2, startingMonth = 2)
+    Timestamp('2019-11-30 05:01:15')
     """
-    _default_starting_month = 3
+    
+    _output_name = "QuarterEnd"
+    _default_month = 3
     _prefix = "Q"
     _day_opt = "end"
 
-    cdef readonly:
-        int _period_dtype_code
-
-    def __init__(self, n=1, normalize=False, startingMonth=None):
-        # Because QuarterEnd can be the freq for a Period, define its
-        #  _period_dtype_code at construction for performance
-        QuarterOffset.__init__(self, n, normalize, startingMonth)
-        self._period_dtype_code = PeriodDtypeCode.Q_DEC + self.startingMonth % 12
-
 
 cdef class QuarterBegin(QuarterOffset):
     """
@@ -2145,9 +2186,23 @@ cdef class QuarterBegin(QuarterOffset):
     startingMonth = 1 corresponds to dates like 1/01/2007, 4/01/2007, ...
     startingMonth = 2 corresponds to dates like 2/01/2007, 5/01/2007, ...
     startingMonth = 3 corresponds to dates like 3/01/2007, 6/01/2007, ...
+            
+    Examples
+    --------
+    >>> from pandas.tseries.offsets import QuarterBegin
+    >>> ts = pd.Timestamp('2020-05-24 05:01:15')
+    >>> ts + QuarterBegin()._from_name('MAR')
+    Timestamp('2020-06-01 05:01:15')
+    >>> ts + QuarterBegin()
+    Timestamp('2020-07-01 05:01:15')
+    >>> ts + QuarterBegin(2)
+    Timestamp('2020-10-01 05:01:15')
+    >>> ts + QuarterBegin(2, startingMonth = 2)
+    Timestamp('2020-11-01 05:01:15')
     """
-    _default_starting_month = 3
-    _from_name_starting_month = 1
+    
+    _output_name = "QuarterBegin"
+    _default_month = 1
     _prefix = "QS"
     _day_opt = "start"
 
@@ -2156,6 +2211,11 @@ cdef class QuarterBegin(QuarterOffset):
 # Month-Based Offset Classes
 
 cdef class MonthOffset(SingleConstructorOffset):
+    cdef readonly:
+        int _period_dtype_code
+        
+    _period_dtype_code = PeriodDtypeCode.M
+    
     def is_on_offset(self, dt: datetime) -> bool:
         if self.normalize and not _is_normalized(dt):
             return False
@@ -2184,22 +2244,43 @@ cdef class MonthOffset(SingleConstructorOffset):
 
         BaseOffset.__setstate__(self, state)
 
+        
+cdef class MonthBegin(MonthOffset):
+    """
+    DateOffset of one month at beginning.
+    """
 
+    _prefix = "MS"
+    _day_opt = "start"
+        
+        
 cdef class MonthEnd(MonthOffset):
     """
     DateOffset of one month end.
     """
-    _period_dtype_code = PeriodDtypeCode.M
+
     _prefix = "M"
     _day_opt = "end"
 
 
-cdef class MonthBegin(MonthOffset):
+cdef class BusinessMonthBegin(MonthOffset):
     """
-    DateOffset of one month at beginning.
+    DateOffset of one month at the first business day.
+
+    Examples
+    --------
+    >>> from pandas.tseries.offset import BMonthBegin
+    >>> ts=pd.Timestamp('2020-05-24 05:01:15')
+    >>> ts + BMonthBegin()
+    Timestamp('2020-06-01 05:01:15')
+    >>> ts + BMonthBegin(2)
+    Timestamp('2020-07-01 05:01:15')
+    >>> ts + BMonthBegin(-3)
+    Timestamp('2020-03-02 05:01:15')
     """
-    _prefix = "MS"
-    _day_opt = "start"
+    
+    _prefix = "BMS"
+    _day_opt = "business_start"
 
 
 cdef class BusinessMonthEnd(MonthOffset):
@@ -2217,29 +2298,11 @@ cdef class BusinessMonthEnd(MonthOffset):
     >>> ts + BMonthEnd(-2)
     Timestamp('2020-03-31 05:01:15')
     """
+    
     _prefix = "BM"
     _day_opt = "business_end"
 
 
-cdef class BusinessMonthBegin(MonthOffset):
-    """
-    DateOffset of one month at the first business day.
-
-    Examples
-    --------
-    >>> from pandas.tseries.offset import BMonthBegin
-    >>> ts=pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + BMonthBegin()
-    Timestamp('2020-06-01 05:01:15')
-    >>> ts + BMonthBegin(2)
-    Timestamp('2020-07-01 05:01:15')
-    >>> ts + BMonthBegin(-3)
-    Timestamp('2020-03-02 05:01:15')
-    """
-    _prefix = "BMS"
-    _day_opt = "business_start"
-
-
 # ---------------------------------------------------------------------
 # Semi-Month Based Offsets
 

From 87e1b87610ccd1e0e430d739d6eebc50aa1481bd Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Wed, 17 Feb 2021 23:32:00 +0100
Subject: [PATCH 02/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 14dac644442a1..5c73c373e73ff 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1840,9 +1840,11 @@ cdef class YearOffset(SingleConstructorOffset):
     """
     
     _attributes = tuple(["n", "normalize", "month"])
+    _default_month = 1
+    _period_dtype_code = None
 
     cdef readonly:
-        int month, _default_month, _period_dtype_code
+        int month
 
     def __init__(self, n=1, normalize=False, month=None):
         BaseOffset.__init__(self, n, normalize)
@@ -2019,14 +2021,19 @@ cdef class BYearEnd(YearOffset):
 # Quarter-Based Offset Classes
 
 cdef class QuarterOffset(SingleConstructorOffset):
-    _attributes = tuple(["n", "normalize", "startingMonth"])
+    """
+    The baseline quarterly DateOffset that just needs a month.
+    """
     # TODO: Consider combining QuarterOffset and YearOffset __init__ at some
     #       point.  Also apply_index, is_on_offset, rule_code if
     #       startingMonth vs month attr names are resolved
-
+    
+    _attributes = tuple(["n", "normalize", "startingMonth"])
+    _default_month = 1
+    _period_dtype_code = None
 
     cdef readonly:
-        int startingMonth, _default_month, _period_dtype_code
+        int startingMonth
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
         BaseOffset.__init__(self, n, normalize)
@@ -2211,9 +2218,6 @@ cdef class QuarterBegin(QuarterOffset):
 # Month-Based Offset Classes
 
 cdef class MonthOffset(SingleConstructorOffset):
-    cdef readonly:
-        int _period_dtype_code
-        
     _period_dtype_code = PeriodDtypeCode.M
     
     def is_on_offset(self, dt: datetime) -> bool:

From 5d46697334e3264b72d9b5205d782c44b576e5f9 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 00:07:46 +0100
Subject: [PATCH 03/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 126 ++++++++++++++++----------------
 1 file changed, 63 insertions(+), 63 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 5c73c373e73ff..de5579e9bdfd7 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1840,8 +1840,8 @@ cdef class YearOffset(SingleConstructorOffset):
     """
     
     _attributes = tuple(["n", "normalize", "month"])
-    _default_month = 1
-    _period_dtype_code = None
+    cdef _default_month int = 1
+    cdef _period_dtype_code int = None
 
     cdef readonly:
         int month
@@ -1853,7 +1853,7 @@ cdef class YearOffset(SingleConstructorOffset):
         self.month = month
 
         if month < 1 or month > 12:
-            raise ValueError("Month must go from 1 to 12")
+            raise ValueError("Month must go from 1 to 12.")
             
         self._period_dtype_code = PeriodDtypeCode.A + self.month % 12
 
@@ -2029,8 +2029,8 @@ cdef class QuarterOffset(SingleConstructorOffset):
     #       startingMonth vs month attr names are resolved
     
     _attributes = tuple(["n", "normalize", "startingMonth"])
-    _default_month = 1
-    _period_dtype_code = None
+    cdef _default_month int = 1
+    cdef _period_dtype_code int = None
 
     cdef readonly:
         int startingMonth
@@ -2040,7 +2040,7 @@ cdef class QuarterOffset(SingleConstructorOffset):
        
         if startingMonth is not None:
             if startingMonth < 1 or startingMonth > 12:
-                raise ValueError("Month must go from 1 to 12") 
+                raise ValueError("Month must go from 1 to 12.") 
             self.startingMonth = startingMonth
         else:
             self.startingMonth = self._default_month
@@ -2101,62 +2101,34 @@ cdef class QuarterOffset(SingleConstructorOffset):
         )
         return shifted
 
-
-cdef class BQuarterEnd(QuarterOffset):
-    """
-    DateOffset increments between the last business day of each Quarter.
-
-    startingMonth = 1 corresponds to dates like 1/31/2007, 4/30/2007, ...
-    startingMonth = 2 corresponds to dates like 2/28/2007, 5/31/2007, ...
-    startingMonth = 3 corresponds to dates like 3/30/2007, 6/29/2007, ...
-
-    Examples
-    --------
-    >>> from pandas.tseries.offsets import BQuarterEnd
-    >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + BQuarterEnd()
-    Timestamp('2020-06-30 05:01:15')
-    >>> ts + BQuarterEnd(2)
-    Timestamp('2020-09-30 05:01:15')
-    >>> ts + BQuarterEnd(1, startingMonth=2)
-    Timestamp('2020-05-29 05:01:15')
-    >>> ts + BQuarterEnd(startingMonth=2)
-    Timestamp('2020-05-29 05:01:15')
-    """
     
-    _output_name = "BusinessQuarterEnd"
-    _default_month = 3
-    _prefix = "BQ"
-    _day_opt = "business_end"
-
-
-cdef class BQuarterBegin(QuarterOffset):
+cdef class QuarterBegin(QuarterOffset):
     """
-    DateOffset increments between the first business day of each Quarter.
+    DateOffset increments between Quarter start dates.
 
     startingMonth = 1 corresponds to dates like 1/01/2007, 4/01/2007, ...
     startingMonth = 2 corresponds to dates like 2/01/2007, 5/01/2007, ...
     startingMonth = 3 corresponds to dates like 3/01/2007, 6/01/2007, ...
-
+            
     Examples
     --------
-    >>> from pandas.tseries.offsets import BQuarterBegin
+    >>> from pandas.tseries.offsets import QuarterBegin
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + BQuarterBegin()
+    >>> ts + QuarterBegin()._from_name('MAR')
+    Timestamp('2020-06-01 05:01:15')
+    >>> ts + QuarterBegin()
     Timestamp('2020-07-01 05:01:15')
-    >>> ts + BQuarterBegin(2)
+    >>> ts + QuarterBegin(2)
     Timestamp('2020-10-01 05:01:15')
-    >>> ts + BQuarterBegin(startingMonth=2)
-    Timestamp('2020-08-03 05:01:15')
-    >>> ts + BQuarterBegin(-1)
-    Timestamp('2020-04-01 05:01:15')
+    >>> ts + QuarterBegin(2, startingMonth = 2)
+    Timestamp('2020-11-01 05:01:15')
     """
     
-    _output_name = "BusinessQuarterBegin"
+    _output_name = "QuarterBegin"
     _default_month = 1
-    _prefix = "BQS"
-    _day_opt = "business_start"
-
+    _prefix = "QS"
+    _day_opt = "start"
+    
 
 cdef class QuarterEnd(QuarterOffset):
     """
@@ -2184,34 +2156,62 @@ cdef class QuarterEnd(QuarterOffset):
     _default_month = 3
     _prefix = "Q"
     _day_opt = "end"
+  
 
-
-cdef class QuarterBegin(QuarterOffset):
+cdef class BQuarterBegin(QuarterOffset):
     """
-    DateOffset increments between Quarter start dates.
+    DateOffset increments between the first business day of each Quarter.
 
     startingMonth = 1 corresponds to dates like 1/01/2007, 4/01/2007, ...
     startingMonth = 2 corresponds to dates like 2/01/2007, 5/01/2007, ...
     startingMonth = 3 corresponds to dates like 3/01/2007, 6/01/2007, ...
-            
+
     Examples
     --------
-    >>> from pandas.tseries.offsets import QuarterBegin
+    >>> from pandas.tseries.offsets import BQuarterBegin
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + QuarterBegin()._from_name('MAR')
-    Timestamp('2020-06-01 05:01:15')
-    >>> ts + QuarterBegin()
+    >>> ts + BQuarterBegin()
     Timestamp('2020-07-01 05:01:15')
-    >>> ts + QuarterBegin(2)
+    >>> ts + BQuarterBegin(2)
     Timestamp('2020-10-01 05:01:15')
-    >>> ts + QuarterBegin(2, startingMonth = 2)
-    Timestamp('2020-11-01 05:01:15')
+    >>> ts + BQuarterBegin(startingMonth=2)
+    Timestamp('2020-08-03 05:01:15')
+    >>> ts + BQuarterBegin(-1)
+    Timestamp('2020-04-01 05:01:15')
     """
     
-    _output_name = "QuarterBegin"
+    _output_name = "BusinessQuarterBegin"
     _default_month = 1
-    _prefix = "QS"
-    _day_opt = "start"
+    _prefix = "BQS"
+    _day_opt = "business_start"
+
+    
+cdef class BQuarterEnd(QuarterOffset):
+    """
+    DateOffset increments between the last business day of each Quarter.
+
+    startingMonth = 1 corresponds to dates like 1/31/2007, 4/30/2007, ...
+    startingMonth = 2 corresponds to dates like 2/28/2007, 5/31/2007, ...
+    startingMonth = 3 corresponds to dates like 3/30/2007, 6/29/2007, ...
+
+    Examples
+    --------
+    >>> from pandas.tseries.offsets import BQuarterEnd
+    >>> ts = pd.Timestamp('2020-05-24 05:01:15')
+    >>> ts + BQuarterEnd()
+    Timestamp('2020-06-30 05:01:15')
+    >>> ts + BQuarterEnd(2)
+    Timestamp('2020-09-30 05:01:15')
+    >>> ts + BQuarterEnd(1, startingMonth=2)
+    Timestamp('2020-05-29 05:01:15')
+    >>> ts + BQuarterEnd(startingMonth=2)
+    Timestamp('2020-05-29 05:01:15')
+    """
+    
+    _output_name = "BusinessQuarterEnd"
+    _default_month = 3
+    _prefix = "BQ"
+    _day_opt = "business_end"
 
 
 # ----------------------------------------------------------------------
@@ -2328,7 +2328,7 @@ cdef class SemiMonthOffset(SingleConstructorOffset):
         if not self._min_day_of_month <= self.day_of_month <= 27:
             raise ValueError(
                 "day_of_month must be "
-                f"{self._min_day_of_month}<=day_of_month<=27, "
+                f"{self._min_day_of_month} <= day_of_month <= 27, "
                 f"got {self.day_of_month}"
             )
 

From a58390560b98fe4c78ea62f514ff5d8dcb754069 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 00:11:24 +0100
Subject: [PATCH 04/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index de5579e9bdfd7..fb30e4067c3ea 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1840,8 +1840,7 @@ cdef class YearOffset(SingleConstructorOffset):
     """
     
     _attributes = tuple(["n", "normalize", "month"])
-    cdef _default_month int = 1
-    cdef _period_dtype_code int = None
+    cdef int _default_month, _period_dtype_code
 
     cdef readonly:
         int month
@@ -2029,8 +2028,7 @@ cdef class QuarterOffset(SingleConstructorOffset):
     #       startingMonth vs month attr names are resolved
     
     _attributes = tuple(["n", "normalize", "startingMonth"])
-    cdef _default_month int = 1
-    cdef _period_dtype_code int = None
+    cdef int _default_month, _period_dtype_code
 
     cdef readonly:
         int startingMonth

From cd216aeb79139fb51bcd7fee4fd8a030cf9ea2ab Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 00:13:43 +0100
Subject: [PATCH 05/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index fb30e4067c3ea..6312f4b6a3a1d 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1840,7 +1840,8 @@ cdef class YearOffset(SingleConstructorOffset):
     """
     
     _attributes = tuple(["n", "normalize", "month"])
-    cdef int _default_month, _period_dtype_code
+    _default_month = 1
+    cdef int _period_dtype_code
 
     cdef readonly:
         int month
@@ -2028,7 +2029,8 @@ cdef class QuarterOffset(SingleConstructorOffset):
     #       startingMonth vs month attr names are resolved
     
     _attributes = tuple(["n", "normalize", "startingMonth"])
-    cdef int _default_month, _period_dtype_code
+    _default_month = 1
+    cdef int _period_dtype_code
 
     cdef readonly:
         int startingMonth

From 53b09c19e9b77edc0c4bb98b51b356c966e15443 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 01:10:29 +0100
Subject: [PATCH 06/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 6312f4b6a3a1d..8b03a9e0f641e 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1841,10 +1841,9 @@ cdef class YearOffset(SingleConstructorOffset):
     
     _attributes = tuple(["n", "normalize", "month"])
     _default_month = 1
-    cdef int _period_dtype_code
+    cdef public int _period_dtype_code
 
-    cdef readonly:
-        int month
+    cdef readonly int month
 
     def __init__(self, n=1, normalize=False, month=None):
         BaseOffset.__init__(self, n, normalize)
@@ -2030,10 +2029,9 @@ cdef class QuarterOffset(SingleConstructorOffset):
     
     _attributes = tuple(["n", "normalize", "startingMonth"])
     _default_month = 1
-    cdef int _period_dtype_code
+    cdef public int _period_dtype_code
 
-    cdef readonly:
-        int startingMonth
+    cdef readonly int startingMonth
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
         BaseOffset.__init__(self, n, normalize)

From 6fdb0afa61882b88cd49b44d09c979b5f2774608 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 07:51:33 +0100
Subject: [PATCH 07/64] Update offsets.pyx

Minor formatting changes.
---
 pandas/_libs/tslibs/offsets.pyx | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 8b03a9e0f641e..cbed3584a1eff 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1841,9 +1841,11 @@ cdef class YearOffset(SingleConstructorOffset):
     
     _attributes = tuple(["n", "normalize", "month"])
     _default_month = 1
-    cdef public int _period_dtype_code
+    cdef public:
+        int _period_dtype_code
 
-    cdef readonly int month
+    cdef readonly:
+        int month
 
     def __init__(self, n=1, normalize=False, month=None):
         BaseOffset.__init__(self, n, normalize)
@@ -2029,9 +2031,11 @@ cdef class QuarterOffset(SingleConstructorOffset):
     
     _attributes = tuple(["n", "normalize", "startingMonth"])
     _default_month = 1
-    cdef public int _period_dtype_code
+    cdef public:
+        int _period_dtype_code
 
-    cdef readonly int startingMonth
+    cdef readonly:
+        int startingMonth
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
         BaseOffset.__init__(self, n, normalize)

From b7d671b3179332d6fb96620c9893e43aaa7574ba Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 08:36:00 +0100
Subject: [PATCH 08/64] Update offsets.pyx

Minor formatting changes.
---
 pandas/_libs/tslibs/offsets.pyx | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index cbed3584a1eff..6d3eebf967ce4 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1841,11 +1841,10 @@ cdef class YearOffset(SingleConstructorOffset):
     
     _attributes = tuple(["n", "normalize", "month"])
     _default_month = 1
-    cdef public:
-        int _period_dtype_code
-
-    cdef readonly:
-        int month
+    
+    cdef:
+        public int _period_dtype_code
+        readonly int month
 
     def __init__(self, n=1, normalize=False, month=None):
         BaseOffset.__init__(self, n, normalize)
@@ -2031,11 +2030,10 @@ cdef class QuarterOffset(SingleConstructorOffset):
     
     _attributes = tuple(["n", "normalize", "startingMonth"])
     _default_month = 1
-    cdef public:
-        int _period_dtype_code
-
-    cdef readonly:
-        int startingMonth
+    
+    cdef:
+        public int _period_dtype_code
+        readonly int startingMonth
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
         BaseOffset.__init__(self, n, normalize)

From de720738a34b251aebd7cebe87ffc82f07854371 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 10:03:19 +0100
Subject: [PATCH 09/64] Add ability to provide months as short names

---
 pandas/_libs/tslibs/offsets.pyx | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 6d3eebf967ce4..580cf1eb81ef0 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2039,6 +2039,8 @@ cdef class QuarterOffset(SingleConstructorOffset):
         BaseOffset.__init__(self, n, normalize)
        
         if startingMonth is not None:
+            if isinstance(startingMonth, str):
+                startingMonth = MONTH_TO_CAL_NUM[suffix]
             if startingMonth < 1 or startingMonth > 12:
                 raise ValueError("Month must go from 1 to 12.") 
             self.startingMonth = startingMonth

From bfaf6ce75a65eb45ff8c9dcec6c99034622f7d80 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 10:05:20 +0100
Subject: [PATCH 10/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 580cf1eb81ef0..189b22e96152c 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2040,7 +2040,7 @@ cdef class QuarterOffset(SingleConstructorOffset):
        
         if startingMonth is not None:
             if isinstance(startingMonth, str):
-                startingMonth = MONTH_TO_CAL_NUM[suffix]
+                startingMonth = MONTH_TO_CAL_NUM[startingMonth]
             if startingMonth < 1 or startingMonth > 12:
                 raise ValueError("Month must go from 1 to 12.") 
             self.startingMonth = startingMonth

From 1b396dde78110eab1eb6e468bea8b3f0faacee29 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 10:16:35 +0100
Subject: [PATCH 11/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 189b22e96152c..321c870cf9283 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1849,11 +1849,14 @@ cdef class YearOffset(SingleConstructorOffset):
     def __init__(self, n=1, normalize=False, month=None):
         BaseOffset.__init__(self, n, normalize)
 
-        month = month if month is not None else self._default_month
-        self.month = month
-
-        if month < 1 or month > 12:
-            raise ValueError("Month must go from 1 to 12.")
+        if month is not None:
+            if isinstance(month, str):
+                month = MONTH_TO_CAL_NUM[month]
+            if month < 1 or month > 12:
+                raise ValueError("Month must go from 1 to 12.") 
+            self.month = month
+        else:
+            self.month = self._default_month
             
         self._period_dtype_code = PeriodDtypeCode.A + self.month % 12
 

From d7f702024b1669433e59fe05bd2bc40c5c8706bd Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 10:45:06 +0100
Subject: [PATCH 12/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 321c870cf9283..cae19a6f49202 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1851,10 +1851,11 @@ cdef class YearOffset(SingleConstructorOffset):
 
         if month is not None:
             if isinstance(month, str):
-                month = MONTH_TO_CAL_NUM[month]
-            if month < 1 or month > 12:
+                self.month = MONTH_TO_CAL_NUM[month]
+            elif month >= 1 and month <= 12:
+                self.month = month
+            else:
                 raise ValueError("Month must go from 1 to 12.") 
-            self.month = month
         else:
             self.month = self._default_month
             
@@ -2043,10 +2044,11 @@ cdef class QuarterOffset(SingleConstructorOffset):
        
         if startingMonth is not None:
             if isinstance(startingMonth, str):
-                startingMonth = MONTH_TO_CAL_NUM[startingMonth]
-            if startingMonth < 1 or startingMonth > 12:
+                self.startingMonth = MONTH_TO_CAL_NUM[startingMonth]
+            elif startingMonth >= 1 and startingMonth <= 12:
+                self.startingMonth = startingMonth
+            else:
                 raise ValueError("Month must go from 1 to 12.") 
-            self.startingMonth = startingMonth
         else:
             self.startingMonth = self._default_month
         

From ca67f8ad8a0840a9d4cb42d0c70e4cb1521f107a Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 10:55:06 +0100
Subject: [PATCH 13/64] Update offsets.pyx

Temporary unfixing of the default months for `QuarterBegin` and `BQuarterBegin`.
---
 pandas/_libs/tslibs/offsets.pyx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index cae19a6f49202..ebebf221e2641 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2132,7 +2132,7 @@ cdef class QuarterBegin(QuarterOffset):
     """
     
     _output_name = "QuarterBegin"
-    _default_month = 1
+    _default_month = 3 # 1
     _prefix = "QS"
     _day_opt = "start"
     
@@ -2188,7 +2188,7 @@ cdef class BQuarterBegin(QuarterOffset):
     """
     
     _output_name = "BusinessQuarterBegin"
-    _default_month = 1
+    _default_month = 3 # 1
     _prefix = "BQS"
     _day_opt = "business_start"
 

From e04e27d8a1f1e64603bd0d19566e8ae444554859 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 11:58:58 +0100
Subject: [PATCH 14/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 82 ++++++++++++++++-----------------
 1 file changed, 41 insertions(+), 41 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index ebebf221e2641..1c2c8e4d367c4 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1838,10 +1838,10 @@ cdef class YearOffset(SingleConstructorOffset):
     """
     DateOffset that just needs a month.
     """
-    
+
     _attributes = tuple(["n", "normalize", "month"])
     _default_month = 1
-    
+
     cdef:
         public int _period_dtype_code
         readonly int month
@@ -1855,10 +1855,10 @@ cdef class YearOffset(SingleConstructorOffset):
             elif month >= 1 and month <= 12:
                 self.month = month
             else:
-                raise ValueError("Month must go from 1 to 12.") 
+                raise ValueError("Month must go from 1 to 12.")
         else:
             self.month = self._default_month
-            
+
         self._period_dtype_code = PeriodDtypeCode.A + self.month % 12
 
     cpdef __setstate__(self, state):
@@ -1876,7 +1876,7 @@ cdef class YearOffset(SingleConstructorOffset):
             if cls._default_month is not None:
                 kwargs["month"] = cls._default_month
         return cls(**kwargs)
-    
+
     @property
     def rule_code(self) -> str:
         month = MONTH_ALIASES[self.month]
@@ -1912,11 +1912,11 @@ cdef class YearOffset(SingleConstructorOffset):
         )
         return shifted
 
-    
+
 cdef class YearBegin(YearOffset):
     """
     DateOffset increments between calendar year begin dates.
-    
+
     Examples
     --------
     >>> from pandas.tseries.offsets import YearBegin
@@ -1933,12 +1933,12 @@ cdef class YearBegin(YearOffset):
     _default_month = 1
     _prefix = "AS"
     _day_opt = "start"
-    
+
 
 cdef class YearEnd(YearOffset):
     """
     DateOffset increments between calendar year ends.
-    
+
     Examples
     --------
     >>> from pandas.tseries.offsets import YearEnd
@@ -1955,8 +1955,8 @@ cdef class YearEnd(YearOffset):
     _default_month = 12
     _prefix = "A"
     _day_opt = "end"
-    
-    
+
+
 cdef class BYearBegin(YearOffset):
     """
     DateOffset increments between the first business day of the year.
@@ -1979,24 +1979,24 @@ cdef class BYearBegin(YearOffset):
     _default_month = 1
     _prefix = "BAS"
     _day_opt = "business_start"
-    
+
 
 cdef class BYearEnd(YearOffset):
     """
     DateOffset increments between the last business days of offset years.
     Here, the year is a period of 12 consecutive calendar months
-    (January - December by default). The "month" parameter allows custom setting 
-    of the final month in a year (and correspondingly - the year start month). 
-    
+    (January - December by default). The "month" parameter allows custom setting
+    of the final month in a year (and correspondingly - the year start month).
+
     Parameters
     ----------
     n : int, default 1
         Number of years to offset.
     normalize: bool, default False
-        If true, the time component of the resulting date-time is converted to 
+        If true, the time component of the resulting date-time is converted to
         00:00:00, i.e. midnight (the start, not the end of date-time).
     month: int, default 12
-        The calendar month number (12 for December) of the ending month 
+        The calendar month number (12 for December) of the ending month
         in a custom-defined year to be used as offset.
 
     Examples
@@ -2019,7 +2019,7 @@ cdef class BYearEnd(YearOffset):
     _default_month = 12
     _prefix = "BA"
     _day_opt = "business_end"
-    
+
 
 # ----------------------------------------------------------------------
 # Quarter-Based Offset Classes
@@ -2031,27 +2031,27 @@ cdef class QuarterOffset(SingleConstructorOffset):
     # TODO: Consider combining QuarterOffset and YearOffset __init__ at some
     #       point.  Also apply_index, is_on_offset, rule_code if
     #       startingMonth vs month attr names are resolved
-    
+
     _attributes = tuple(["n", "normalize", "startingMonth"])
     _default_month = 1
-    
+
     cdef:
         public int _period_dtype_code
         readonly int startingMonth
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
         BaseOffset.__init__(self, n, normalize)
-       
+
         if startingMonth is not None:
             if isinstance(startingMonth, str):
                 self.startingMonth = MONTH_TO_CAL_NUM[startingMonth]
             elif startingMonth >= 1 and startingMonth <= 12:
                 self.startingMonth = startingMonth
             else:
-                raise ValueError("Month must go from 1 to 12.") 
+                raise ValueError("Month must go from 1 to 12.")
         else:
             self.startingMonth = self._default_month
-        
+
         self._period_dtype_code = PeriodDtypeCode.Q_DEC + self.startingMonth % 12
 
     cpdef __setstate__(self, state):
@@ -2108,7 +2108,7 @@ cdef class QuarterOffset(SingleConstructorOffset):
         )
         return shifted
 
-    
+
 cdef class QuarterBegin(QuarterOffset):
     """
     DateOffset increments between Quarter start dates.
@@ -2116,7 +2116,7 @@ cdef class QuarterBegin(QuarterOffset):
     startingMonth = 1 corresponds to dates like 1/01/2007, 4/01/2007, ...
     startingMonth = 2 corresponds to dates like 2/01/2007, 5/01/2007, ...
     startingMonth = 3 corresponds to dates like 3/01/2007, 6/01/2007, ...
-            
+
     Examples
     --------
     >>> from pandas.tseries.offsets import QuarterBegin
@@ -2130,12 +2130,12 @@ cdef class QuarterBegin(QuarterOffset):
     >>> ts + QuarterBegin(2, startingMonth = 2)
     Timestamp('2020-11-01 05:01:15')
     """
-    
+
     _output_name = "QuarterBegin"
-    _default_month = 3 # 1
+    _default_month = 1
     _prefix = "QS"
     _day_opt = "start"
-    
+
 
 cdef class QuarterEnd(QuarterOffset):
     """
@@ -2144,7 +2144,7 @@ cdef class QuarterEnd(QuarterOffset):
     startingMonth = 1 corresponds to dates like 1/31/2007, 4/30/2007, ...
     startingMonth = 2 corresponds to dates like 2/28/2007, 5/31/2007, ...
     startingMonth = 3 corresponds to dates like 3/31/2007, 6/30/2007, ...
-    
+
     Examples
     --------
     >>> from pandas.tseries.offsets import QuarterEnd
@@ -2158,12 +2158,12 @@ cdef class QuarterEnd(QuarterOffset):
     >>> ts + QuarterEnd(-2, startingMonth = 2)
     Timestamp('2019-11-30 05:01:15')
     """
-    
+
     _output_name = "QuarterEnd"
     _default_month = 3
     _prefix = "Q"
     _day_opt = "end"
-  
+
 
 cdef class BQuarterBegin(QuarterOffset):
     """
@@ -2186,13 +2186,13 @@ cdef class BQuarterBegin(QuarterOffset):
     >>> ts + BQuarterBegin(-1)
     Timestamp('2020-04-01 05:01:15')
     """
-    
+
     _output_name = "BusinessQuarterBegin"
-    _default_month = 3 # 1
+    _default_month = 1
     _prefix = "BQS"
     _day_opt = "business_start"
 
-    
+
 cdef class BQuarterEnd(QuarterOffset):
     """
     DateOffset increments between the last business day of each Quarter.
@@ -2214,7 +2214,7 @@ cdef class BQuarterEnd(QuarterOffset):
     >>> ts + BQuarterEnd(startingMonth=2)
     Timestamp('2020-05-29 05:01:15')
     """
-    
+
     _output_name = "BusinessQuarterEnd"
     _default_month = 3
     _prefix = "BQ"
@@ -2226,7 +2226,7 @@ cdef class BQuarterEnd(QuarterOffset):
 
 cdef class MonthOffset(SingleConstructorOffset):
     _period_dtype_code = PeriodDtypeCode.M
-    
+
     def is_on_offset(self, dt: datetime) -> bool:
         if self.normalize and not _is_normalized(dt):
             return False
@@ -2255,7 +2255,7 @@ cdef class MonthOffset(SingleConstructorOffset):
 
         BaseOffset.__setstate__(self, state)
 
-        
+
 cdef class MonthBegin(MonthOffset):
     """
     DateOffset of one month at beginning.
@@ -2263,8 +2263,8 @@ cdef class MonthBegin(MonthOffset):
 
     _prefix = "MS"
     _day_opt = "start"
-        
-        
+
+
 cdef class MonthEnd(MonthOffset):
     """
     DateOffset of one month end.
@@ -2289,7 +2289,7 @@ cdef class BusinessMonthBegin(MonthOffset):
     >>> ts + BMonthBegin(-3)
     Timestamp('2020-03-02 05:01:15')
     """
-    
+
     _prefix = "BMS"
     _day_opt = "business_start"
 
@@ -2309,7 +2309,7 @@ cdef class BusinessMonthEnd(MonthOffset):
     >>> ts + BMonthEnd(-2)
     Timestamp('2020-03-31 05:01:15')
     """
-    
+
     _prefix = "BM"
     _day_opt = "business_end"
 

From d4d87c4725fec0ce82fc1f449221015d5dc8a498 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 12:12:38 +0100
Subject: [PATCH 15/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 1c2c8e4d367c4..2102fa891f5cb 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2132,7 +2132,7 @@ cdef class QuarterBegin(QuarterOffset):
     """
 
     _output_name = "QuarterBegin"
-    _default_month = 1
+    _default_month = 3 #1
     _prefix = "QS"
     _day_opt = "start"
 
@@ -2188,7 +2188,7 @@ cdef class BQuarterBegin(QuarterOffset):
     """
 
     _output_name = "BusinessQuarterBegin"
-    _default_month = 1
+    _default_month = 3 #1
     _prefix = "BQS"
     _day_opt = "business_start"
 
@@ -2261,6 +2261,7 @@ cdef class MonthBegin(MonthOffset):
     DateOffset of one month at beginning.
     """
 
+    _period_dtype_code = None
     _prefix = "MS"
     _day_opt = "start"
 

From 2c22a3171239006b9a62fd8643abef8f4300c6b4 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 12:26:16 +0100
Subject: [PATCH 16/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 2102fa891f5cb..a02d1df9be3cf 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2132,7 +2132,7 @@ cdef class QuarterBegin(QuarterOffset):
     """
 
     _output_name = "QuarterBegin"
-    _default_month = 3 #1
+    _default_month = 3  # should be 1
     _prefix = "QS"
     _day_opt = "start"
 
@@ -2188,7 +2188,7 @@ cdef class BQuarterBegin(QuarterOffset):
     """
 
     _output_name = "BusinessQuarterBegin"
-    _default_month = 3 #1
+    _default_month = 3  # Should be 1
     _prefix = "BQS"
     _day_opt = "business_start"
 

From 11cb0b51403834394de6850710193c20fd054fe5 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 13:29:33 +0100
Subject: [PATCH 17/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index a02d1df9be3cf..281ff1ed010ec 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1992,10 +1992,10 @@ cdef class BYearEnd(YearOffset):
     ----------
     n : int, default 1
         Number of years to offset.
-    normalize: bool, default False
+    normalize : bool, default False
         If true, the time component of the resulting date-time is converted to
         00:00:00, i.e. midnight (the start, not the end of date-time).
-    month: int, default 12
+    month : int, default 12
         The calendar month number (12 for December) of the ending month
         in a custom-defined year to be used as offset.
 
@@ -2261,7 +2261,7 @@ cdef class MonthBegin(MonthOffset):
     DateOffset of one month at beginning.
     """
 
-    _period_dtype_code = None
+    del(_period_dtype_code)
     _prefix = "MS"
     _day_opt = "start"
 

From 71e9cab775502f31c2450a42521aa388d84e7c18 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 13:40:13 +0100
Subject: [PATCH 18/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 281ff1ed010ec..9858009c99711 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2225,7 +2225,7 @@ cdef class BQuarterEnd(QuarterOffset):
 # Month-Based Offset Classes
 
 cdef class MonthOffset(SingleConstructorOffset):
-    _period_dtype_code = PeriodDtypeCode.M
+    # _period_dtype_code = PeriodDtypeCode.M
 
     def is_on_offset(self, dt: datetime) -> bool:
         if self.normalize and not _is_normalized(dt):
@@ -2261,7 +2261,6 @@ cdef class MonthBegin(MonthOffset):
     DateOffset of one month at beginning.
     """
 
-    del(_period_dtype_code)
     _prefix = "MS"
     _day_opt = "start"
 
@@ -2271,6 +2270,7 @@ cdef class MonthEnd(MonthOffset):
     DateOffset of one month end.
     """
 
+    _period_dtype_code = M
     _prefix = "M"
     _day_opt = "end"
 
@@ -2311,6 +2311,7 @@ cdef class BusinessMonthEnd(MonthOffset):
     Timestamp('2020-03-31 05:01:15')
     """
 
+    _period_dtype_code = M
     _prefix = "BM"
     _day_opt = "business_end"
 

From 29edef378c3939c34eb420a62658eb2e9bdc9e01 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 13:42:08 +0100
Subject: [PATCH 19/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 9858009c99711..608d95d322c7c 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2270,7 +2270,7 @@ cdef class MonthEnd(MonthOffset):
     DateOffset of one month end.
     """
 
-    _period_dtype_code = M
+    _period_dtype_code = PeriodDtypeCode.M
     _prefix = "M"
     _day_opt = "end"
 
@@ -2311,7 +2311,7 @@ cdef class BusinessMonthEnd(MonthOffset):
     Timestamp('2020-03-31 05:01:15')
     """
 
-    _period_dtype_code = M
+    _period_dtype_code = PeriodDtypeCode.M
     _prefix = "BM"
     _day_opt = "business_end"
 

From 485e60b9c0bfa8fe816e930b566ceaae1e56dbc4 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 17:35:57 +0100
Subject: [PATCH 20/64] [BUG] Breaking change to offsets.pyx - MonthOffset

Add ability to use `MonthBegin`, `BMonthBegin` and `BMonthEnd` as periods, e.g., by using their offset aliases as `freq` in `date_range`.
It would address #38914.
---
 pandas/_libs/tslibs/offsets.pyx | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 2d4704ad3bda6..771230fe794eb 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2156,6 +2156,8 @@ cdef class QuarterBegin(QuarterOffset):
 # Month-Based Offset Classes
 
 cdef class MonthOffset(SingleConstructorOffset):
+    _period_dtype_code = PeriodDtypeCode.M
+
     def is_on_offset(self, dt: datetime) -> bool:
         if self.normalize and not _is_normalized(dt):
             return False
@@ -2189,7 +2191,6 @@ cdef class MonthEnd(MonthOffset):
     """
     DateOffset of one month end.
     """
-    _period_dtype_code = PeriodDtypeCode.M
     _prefix = "M"
     _day_opt = "end"
 

From 0fa3644bad22076f63c17fe93ab3b74034e57d21 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 20:29:03 +0100
Subject: [PATCH 21/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 608d95d322c7c..4bb4e4e9f53c9 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2123,10 +2123,6 @@ cdef class QuarterBegin(QuarterOffset):
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
     >>> ts + QuarterBegin()._from_name('MAR')
     Timestamp('2020-06-01 05:01:15')
-    >>> ts + QuarterBegin()
-    Timestamp('2020-07-01 05:01:15')
-    >>> ts + QuarterBegin(2)
-    Timestamp('2020-10-01 05:01:15')
     >>> ts + QuarterBegin(2, startingMonth = 2)
     Timestamp('2020-11-01 05:01:15')
     """
@@ -2135,6 +2131,17 @@ cdef class QuarterBegin(QuarterOffset):
     _default_month = 3  # should be 1
     _prefix = "QS"
     _day_opt = "start"
+    _from_name_starting_month = 1
+
+    @classmethod
+    def _from_name(cls, suffix=None):
+        kwargs = {}
+        if suffix:
+            kwargs["startingMonth"] = MONTH_TO_CAL_NUM[suffix]
+        else:
+            if cls._from_name_starting_month is not None:
+                kwargs["startingMonth"] = cls._from_name_starting_month
+        return cls(**kwargs)
 
 
 cdef class QuarterEnd(QuarterOffset):
@@ -2177,20 +2184,25 @@ cdef class BQuarterBegin(QuarterOffset):
     --------
     >>> from pandas.tseries.offsets import BQuarterBegin
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + BQuarterBegin()
-    Timestamp('2020-07-01 05:01:15')
-    >>> ts + BQuarterBegin(2)
-    Timestamp('2020-10-01 05:01:15')
     >>> ts + BQuarterBegin(startingMonth=2)
     Timestamp('2020-08-03 05:01:15')
-    >>> ts + BQuarterBegin(-1)
-    Timestamp('2020-04-01 05:01:15')
     """
 
     _output_name = "BusinessQuarterBegin"
     _default_month = 3  # Should be 1
     _prefix = "BQS"
     _day_opt = "business_start"
+    _from_name_starting_month = 1
+
+    @classmethod
+    def _from_name(cls, suffix=None):
+        kwargs = {}
+        if suffix:
+            kwargs["startingMonth"] = MONTH_TO_CAL_NUM[suffix]
+        else:
+            if cls._from_name_starting_month is not None:
+                kwargs["startingMonth"] = cls._from_name_starting_month
+        return cls(**kwargs)
 
 
 cdef class BQuarterEnd(QuarterOffset):

From 3456f5a5029a734729c8eed2275014fa6eb999dc Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 21:02:10 +0100
Subject: [PATCH 22/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 4bb4e4e9f53c9..4db7ec5139c2b 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2228,7 +2228,7 @@ cdef class BQuarterEnd(QuarterOffset):
     """
 
     _output_name = "BusinessQuarterEnd"
-    _default_month = 3
+    _default_month = 12  # Should be 3
     _prefix = "BQ"
     _day_opt = "business_end"
 

From 564cd299ecc4b754c2533656130cf005653864fe Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 21:37:29 +0100
Subject: [PATCH 23/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 31 ++++++-------------------------
 1 file changed, 6 insertions(+), 25 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 4db7ec5139c2b..b5267edab4352 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2065,8 +2065,8 @@ cdef class QuarterOffset(SingleConstructorOffset):
         if suffix:
             kwargs["startingMonth"] = MONTH_TO_CAL_NUM[suffix]
         else:
-            if cls._default_month is not None:
-                kwargs["startingMonth"] = cls._default_month
+            if cls._from_name_starting_month is not None:
+                kwargs["startingMonth"] = cls._from_name_starting_month
         return cls(**kwargs)
 
     @property
@@ -2129,19 +2129,9 @@ cdef class QuarterBegin(QuarterOffset):
 
     _output_name = "QuarterBegin"
     _default_month = 3  # should be 1
+    _from_name_starting_month = 1
     _prefix = "QS"
     _day_opt = "start"
-    _from_name_starting_month = 1
-
-    @classmethod
-    def _from_name(cls, suffix=None):
-        kwargs = {}
-        if suffix:
-            kwargs["startingMonth"] = MONTH_TO_CAL_NUM[suffix]
-        else:
-            if cls._from_name_starting_month is not None:
-                kwargs["startingMonth"] = cls._from_name_starting_month
-        return cls(**kwargs)
 
 
 cdef class QuarterEnd(QuarterOffset):
@@ -2190,19 +2180,9 @@ cdef class BQuarterBegin(QuarterOffset):
 
     _output_name = "BusinessQuarterBegin"
     _default_month = 3  # Should be 1
+    _from_name_starting_month = 1
     _prefix = "BQS"
     _day_opt = "business_start"
-    _from_name_starting_month = 1
-
-    @classmethod
-    def _from_name(cls, suffix=None):
-        kwargs = {}
-        if suffix:
-            kwargs["startingMonth"] = MONTH_TO_CAL_NUM[suffix]
-        else:
-            if cls._from_name_starting_month is not None:
-                kwargs["startingMonth"] = cls._from_name_starting_month
-        return cls(**kwargs)
 
 
 cdef class BQuarterEnd(QuarterOffset):
@@ -2228,7 +2208,8 @@ cdef class BQuarterEnd(QuarterOffset):
     """
 
     _output_name = "BusinessQuarterEnd"
-    _default_month = 12  # Should be 3
+    _default_month = 3
+    _from_name_starting_month = 12
     _prefix = "BQ"
     _day_opt = "business_end"
 

From 926745d4047fc4ef4415c9c79ef8475063fabac5 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Feb 2021 22:37:45 +0100
Subject: [PATCH 24/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index b5267edab4352..2bbac51ad0756 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2201,7 +2201,7 @@ cdef class BQuarterEnd(QuarterOffset):
     Timestamp('2020-06-30 05:01:15')
     >>> ts + BQuarterEnd(2)
     Timestamp('2020-09-30 05:01:15')
-    >>> ts + BQuarterEnd(1, startingMonth=2)
+    >>> ts + BQuarterEnd(1, startingMonth = 2)
     Timestamp('2020-05-29 05:01:15')
     >>> ts + BQuarterEnd(startingMonth=2)
     Timestamp('2020-05-29 05:01:15')

From 4593d7295c3882f77351e2094d6d40e47aec3602 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 09:34:43 +0100
Subject: [PATCH 25/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 771230fe794eb..890e2c1304d5d 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -3471,6 +3471,8 @@ _lite_rule_alias = {
     "BAS": "BAS-JAN",  # BYearBegin(month=1),
     "BYS": "BAS-JAN",
 
+    "MS": "M"
+
     "Min": "T",
     "min": "T",
     "ms": "L",

From 85c896ce6c4c5aac33101cd636777461b3e43ff6 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 09:39:04 +0100
Subject: [PATCH 26/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 890e2c1304d5d..fd3a19483f456 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -3471,7 +3471,9 @@ _lite_rule_alias = {
     "BAS": "BAS-JAN",  # BYearBegin(month=1),
     "BYS": "BAS-JAN",
 
-    "MS": "M"
+    "MS": "M",         # MonthBegin
+    "BMS": "M",        # BusinessMonthBegin
+    "BM": "M",         # BusinessMonthEnd
 
     "Min": "T",
     "min": "T",

From 6654c89bc036cea85d7f6977c1ae381bd8822f1a Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 09:43:32 +0100
Subject: [PATCH 27/64] Update test_asfreq.py

---
 pandas/tests/scalar/period/test_asfreq.py | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/pandas/tests/scalar/period/test_asfreq.py b/pandas/tests/scalar/period/test_asfreq.py
index 9110352d33c26..2b331bea41462 100644
--- a/pandas/tests/scalar/period/test_asfreq.py
+++ b/pandas/tests/scalar/period/test_asfreq.py
@@ -793,12 +793,8 @@ def test_asfreq_MS(self):
         initial = Period("2013")
 
         assert initial.asfreq(freq="M", how="S") == Period("2013-01", "M")
-
-        msg = INVALID_FREQ_ERR_MSG
-        with pytest.raises(ValueError, match=msg):
-            initial.asfreq(freq="MS", how="S")
-
-        with pytest.raises(ValueError, match=msg):
-            Period("2013-01", "MS")
+        assert initial.asfreq(freq="MS", how="S") == Period("2013-01", "MS")
+        assert initial.asfreq(freq="M", how="S") == Period("2013-01", "MS")
+        assert initial.asfreq(freq="MS", how="S") == Period("2013-01", "M")
 
         assert _period_code_map.get("MS") is None

From 527f70f5bd0a27c55f0a3488eb3f4ab1ccae2ddb Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 09:49:24 +0100
Subject: [PATCH 28/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index fd3a19483f456..fea34cbdd0915 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2209,13 +2209,13 @@ cdef class BusinessMonthEnd(MonthOffset):
 
     Examples
     --------
-    >>> from pandas.tseries.offset import BMonthEnd
+    >>> from pandas.tseries.offsets import BusinessMonthEnd
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + BMonthEnd()
+    >>> ts + BusinessMonthEnd()
     Timestamp('2020-05-29 05:01:15')
-    >>> ts + BMonthEnd(2)
+    >>> ts + BusinessMonthEnd(2)
     Timestamp('2020-06-30 05:01:15')
-    >>> ts + BMonthEnd(-2)
+    >>> ts + BusinessMonthEnd(-2)
     Timestamp('2020-03-31 05:01:15')
     """
     _prefix = "BM"
@@ -2228,13 +2228,13 @@ cdef class BusinessMonthBegin(MonthOffset):
 
     Examples
     --------
-    >>> from pandas.tseries.offset import BMonthBegin
+    >>> from pandas.tseries.offsets import BusinessMonthBegin
     >>> ts=pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + BMonthBegin()
+    >>> ts + BusinessMonthBegin()
     Timestamp('2020-06-01 05:01:15')
-    >>> ts + BMonthBegin(2)
+    >>> ts + BusinessMonthBegin(2)
     Timestamp('2020-07-01 05:01:15')
-    >>> ts + BMonthBegin(-3)
+    >>> ts + BusinessMonthBegin(-3)
     Timestamp('2020-03-02 05:01:15')
     """
     _prefix = "BMS"

From 32d61edff23f7ae0386fdbb0eeb415745c301586 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 10:13:19 +0100
Subject: [PATCH 29/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index fea34cbdd0915..a79a5816cea47 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2218,6 +2218,8 @@ cdef class BusinessMonthEnd(MonthOffset):
     >>> ts + BusinessMonthEnd(-2)
     Timestamp('2020-03-31 05:01:15')
     """
+
+    _period_dtype_code = None
     _prefix = "BM"
     _day_opt = "business_end"
 
@@ -2237,6 +2239,8 @@ cdef class BusinessMonthBegin(MonthOffset):
     >>> ts + BusinessMonthBegin(-3)
     Timestamp('2020-03-02 05:01:15')
     """
+
+    _period_dtype_code = None
     _prefix = "BMS"
     _day_opt = "business_start"
 
@@ -3472,8 +3476,9 @@ _lite_rule_alias = {
     "BYS": "BAS-JAN",
 
     "MS": "M",         # MonthBegin
-    "BMS": "M",        # BusinessMonthBegin
-    "BM": "M",         # BusinessMonthEnd
+    # TODO: implement business month periods?
+    # "BMS": "BM",       # BusinessMonthBegin
+    # "BM": "BM",        # BusinessMonthEnd
 
     "Min": "T",
     "min": "T",

From 63325a0a314ea3dcf7b03256a2db9ca3884f3bc0 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 11:47:40 +0100
Subject: [PATCH 30/64] Update offsets.pyx

Rollback of _lite_rule_alias change.
---
 pandas/_libs/tslibs/offsets.pyx | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index a79a5816cea47..ae8d8c3439565 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -3475,11 +3475,6 @@ _lite_rule_alias = {
     "BAS": "BAS-JAN",  # BYearBegin(month=1),
     "BYS": "BAS-JAN",
 
-    "MS": "M",         # MonthBegin
-    # TODO: implement business month periods?
-    # "BMS": "BM",       # BusinessMonthBegin
-    # "BM": "BM",        # BusinessMonthEnd
-
     "Min": "T",
     "min": "T",
     "ms": "L",

From 199237a07af5bde1756407bc4e9252fe2e561138 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 11:49:53 +0100
Subject: [PATCH 31/64] Update dtypes.pyx

Add `"MS"` as a monthly code to `_period_code_map`
---
 pandas/_libs/tslibs/dtypes.pyx | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pandas/_libs/tslibs/dtypes.pyx b/pandas/_libs/tslibs/dtypes.pyx
index 415bdf74db80a..f36ca20558566 100644
--- a/pandas/_libs/tslibs/dtypes.pyx
+++ b/pandas/_libs/tslibs/dtypes.pyx
@@ -78,6 +78,7 @@ _period_code_map = {
     "Q-NOV": 2011,    # Quarterly - November year end
 
     "M": 3000,        # Monthly
+    "MS": 3000,       # Monthly
 
     "W-SUN": 4000,    # Weekly - Sunday end of week
     "W-MON": 4001,    # Weekly - Monday end of week

From cd79bff7ba7fa413e51aa08c00c28b48d2ed97b0 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 12:06:57 +0100
Subject: [PATCH 32/64] Update test_asfreq.py

---
 pandas/tests/scalar/period/test_asfreq.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/tests/scalar/period/test_asfreq.py b/pandas/tests/scalar/period/test_asfreq.py
index 2b331bea41462..952cd6c28b911 100644
--- a/pandas/tests/scalar/period/test_asfreq.py
+++ b/pandas/tests/scalar/period/test_asfreq.py
@@ -791,10 +791,10 @@ def test_asfreq_combined(self):
 
     def test_asfreq_MS(self):
         initial = Period("2013")
+        ts1 = Period("2013-01", "MS").to_timestamp()
+        ts2 = Period("2013-01", "M").to_timestamp(how="start")
 
         assert initial.asfreq(freq="M", how="S") == Period("2013-01", "M")
         assert initial.asfreq(freq="MS", how="S") == Period("2013-01", "MS")
-        assert initial.asfreq(freq="M", how="S") == Period("2013-01", "MS")
-        assert initial.asfreq(freq="MS", how="S") == Period("2013-01", "M")
-
-        assert _period_code_map.get("MS") is None
+        assert initial.asfreq(freq="M", how="S").to_timestamp(how="start") == ts1
+        assert initial.asfreq(freq="MS", how="S").to_timestamp() == ts2

From 42c4e2632ce10197bda2f595c5bb447672489943 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 12:14:10 +0100
Subject: [PATCH 33/64] Update test_asfreq.py

---
 pandas/tests/scalar/period/test_asfreq.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/tests/scalar/period/test_asfreq.py b/pandas/tests/scalar/period/test_asfreq.py
index 952cd6c28b911..2ae40fcf1bb12 100644
--- a/pandas/tests/scalar/period/test_asfreq.py
+++ b/pandas/tests/scalar/period/test_asfreq.py
@@ -796,5 +796,6 @@ def test_asfreq_MS(self):
 
         assert initial.asfreq(freq="M", how="S") == Period("2013-01", "M")
         assert initial.asfreq(freq="MS", how="S") == Period("2013-01", "MS")
-        assert initial.asfreq(freq="M", how="S").to_timestamp(how="start") == ts1
+        assert initial.asfreq(freq="M", how="S").to_timestamp(how="start") \
+            == ts1
         assert initial.asfreq(freq="MS", how="S").to_timestamp() == ts2

From 0ce8c021d767c6a406d2463be99553d867b41421 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 12:26:33 +0100
Subject: [PATCH 34/64] Update test_asfreq.py

---
 pandas/tests/scalar/period/test_asfreq.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/tests/scalar/period/test_asfreq.py b/pandas/tests/scalar/period/test_asfreq.py
index 2ae40fcf1bb12..57f48459c0603 100644
--- a/pandas/tests/scalar/period/test_asfreq.py
+++ b/pandas/tests/scalar/period/test_asfreq.py
@@ -791,11 +791,11 @@ def test_asfreq_combined(self):
 
     def test_asfreq_MS(self):
         initial = Period("2013")
+        ts0 = initial.asfreq(freq="M", how="S").to_timestamp(how="start")
         ts1 = Period("2013-01", "MS").to_timestamp()
         ts2 = Period("2013-01", "M").to_timestamp(how="start")
 
         assert initial.asfreq(freq="M", how="S") == Period("2013-01", "M")
         assert initial.asfreq(freq="MS", how="S") == Period("2013-01", "MS")
-        assert initial.asfreq(freq="M", how="S").to_timestamp(how="start") \
-            == ts1
+        assert ts0 == ts1
         assert initial.asfreq(freq="MS", how="S").to_timestamp() == ts2

From 362d3d163ad68fabd1939db28e610764ec73b2e7 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 12:40:31 +0100
Subject: [PATCH 35/64] Update test_asfreq.py

---
 pandas/tests/scalar/period/test_asfreq.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/pandas/tests/scalar/period/test_asfreq.py b/pandas/tests/scalar/period/test_asfreq.py
index 57f48459c0603..c71c5fb613966 100644
--- a/pandas/tests/scalar/period/test_asfreq.py
+++ b/pandas/tests/scalar/period/test_asfreq.py
@@ -1,6 +1,5 @@
 import pytest
 
-from pandas._libs.tslibs.dtypes import _period_code_map
 from pandas._libs.tslibs.period import INVALID_FREQ_ERR_MSG
 from pandas.errors import OutOfBoundsDatetime
 

From 6f18722dc3c548af923fec8201a270a32b90686c Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 12:55:18 +0100
Subject: [PATCH 36/64] Update test_period.py

---
 pandas/tests/scalar/period/test_period.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pandas/tests/scalar/period/test_period.py b/pandas/tests/scalar/period/test_period.py
index 7dcd4dc979eb2..d9794549d7e2b 100644
--- a/pandas/tests/scalar/period/test_period.py
+++ b/pandas/tests/scalar/period/test_period.py
@@ -220,6 +220,7 @@ def test_period_constructor_offsets(self):
         )
 
         assert Period(200701, freq=offsets.MonthEnd()) == Period(200701, freq="M")
+        assert Period(200701, freq=offsets.MonthBegin()) == Period(200701, freq="MS")
 
         i1 = Period(ordinal=200701, freq=offsets.MonthEnd())
         i2 = Period(ordinal=200701, freq="M")

From 818cbdf638694990f027f950aa150f0fdf36721a Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 19:45:30 +0100
Subject: [PATCH 37/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 2bbac51ad0756..405d2c9df8f6e 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1925,8 +1925,6 @@ cdef class YearBegin(YearOffset):
     Timestamp('2021-01-01 05:01:15')
     >>> ts + YearBegin(normalize = True)
     Timestamp('2021-01-01 00:00:00')
-    >>> ts + YearBegin()._from_name('APR')
-    Timestamp('2021-04-01 05:01:15')
     """
 
     _outputName = "YearBegin"
@@ -1947,8 +1945,6 @@ cdef class YearEnd(YearOffset):
     Timestamp('2020-12-31 05:01:15')
     >>> ts + YearEnd(normalize = True)
     Timestamp('2020-12-31 00:00:00')
-    >>> ts + YearEnd()._from_name('AUG')
-    Timestamp('2020-08-31 05:01:15')
     """
 
     _outputName = "YearEnd"
@@ -1975,6 +1971,7 @@ cdef class BYearBegin(YearOffset):
     Timestamp('2022-01-03 05:01:15')
     """
 
+    _period_dtype_code = None
     _outputName = "BusinessYearBegin"
     _default_month = 1
     _prefix = "BAS"
@@ -2015,6 +2012,7 @@ cdef class BYearEnd(YearOffset):
     Timestamp('2020-11-30 05:01:15')
     """
 
+    _period_dtype_code = None
     _outputName = "BusinessYearEnd"
     _default_month = 12
     _prefix = "BA"
@@ -2121,8 +2119,6 @@ cdef class QuarterBegin(QuarterOffset):
     --------
     >>> from pandas.tseries.offsets import QuarterBegin
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + QuarterBegin()._from_name('MAR')
-    Timestamp('2020-06-01 05:01:15')
     >>> ts + QuarterBegin(2, startingMonth = 2)
     Timestamp('2020-11-01 05:01:15')
     """
@@ -2148,8 +2144,6 @@ cdef class QuarterEnd(QuarterOffset):
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
     >>> ts + QuarterEnd(2)
     Timestamp('2020-09-30 05:01:15')
-    >>> ts + QuarterEnd()._from_name('JUN')
-    Timestamp('2020-06-30 05:01:15')
     >>> ts + QuarterEnd(1, normalize = True)
     Timestamp('2020-06-30 00:00:00')
     >>> ts + QuarterEnd(-2, startingMonth = 2)
@@ -2178,6 +2172,7 @@ cdef class BQuarterBegin(QuarterOffset):
     Timestamp('2020-08-03 05:01:15')
     """
 
+    _period_dtype_code = None
     _output_name = "BusinessQuarterBegin"
     _default_month = 3  # Should be 1
     _from_name_starting_month = 1
@@ -2207,6 +2202,7 @@ cdef class BQuarterEnd(QuarterOffset):
     Timestamp('2020-05-29 05:01:15')
     """
 
+    _period_dtype_code = None
     _output_name = "BusinessQuarterEnd"
     _default_month = 3
     _from_name_starting_month = 12

From 1d14b0fa17920ce20df3b168d0544317a4b7819f Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 20:01:48 +0100
Subject: [PATCH 38/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 405d2c9df8f6e..d5f4f59daeba1 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2172,7 +2172,7 @@ cdef class BQuarterBegin(QuarterOffset):
     Timestamp('2020-08-03 05:01:15')
     """
 
-    _period_dtype_code = None
+    self._period_dtype_code = None
     _output_name = "BusinessQuarterBegin"
     _default_month = 3  # Should be 1
     _from_name_starting_month = 1
@@ -2202,7 +2202,7 @@ cdef class BQuarterEnd(QuarterOffset):
     Timestamp('2020-05-29 05:01:15')
     """
 
-    _period_dtype_code = None
+    self._period_dtype_code = None
     _output_name = "BusinessQuarterEnd"
     _default_month = 3
     _from_name_starting_month = 12

From 700ba0e7744d820aee350f0f2c8cfc0a31bb437a Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 20:31:55 +0100
Subject: [PATCH 39/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index d5f4f59daeba1..273aeb418ddd0 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1843,7 +1843,6 @@ cdef class YearOffset(SingleConstructorOffset):
     _default_month = 1
 
     cdef:
-        public int _period_dtype_code
         readonly int month
 
     def __init__(self, n=1, normalize=False, month=None):
@@ -2034,7 +2033,6 @@ cdef class QuarterOffset(SingleConstructorOffset):
     _default_month = 1
 
     cdef:
-        public int _period_dtype_code
         readonly int startingMonth
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
@@ -2172,7 +2170,7 @@ cdef class BQuarterBegin(QuarterOffset):
     Timestamp('2020-08-03 05:01:15')
     """
 
-    self._period_dtype_code = None
+    _period_dtype_code = None
     _output_name = "BusinessQuarterBegin"
     _default_month = 3  # Should be 1
     _from_name_starting_month = 1
@@ -2202,7 +2200,7 @@ cdef class BQuarterEnd(QuarterOffset):
     Timestamp('2020-05-29 05:01:15')
     """
 
-    self._period_dtype_code = None
+    _period_dtype_code = None
     _output_name = "BusinessQuarterEnd"
     _default_month = 3
     _from_name_starting_month = 12

From 648c7a8d92f033aad3dcd862bb05539159b9d394 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 21:42:06 +0100
Subject: [PATCH 40/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 273aeb418ddd0..146be5538d904 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1840,10 +1840,11 @@ cdef class YearOffset(SingleConstructorOffset):
     """
 
     _attributes = tuple(["n", "normalize", "month"])
-    _default_month = 1
+    # _default_month = 1
 
     cdef:
         readonly int month
+        public int _default_month, _period_dtype_code
 
     def __init__(self, n=1, normalize=False, month=None):
         BaseOffset.__init__(self, n, normalize)
@@ -1970,7 +1971,7 @@ cdef class BYearBegin(YearOffset):
     Timestamp('2022-01-03 05:01:15')
     """
 
-    _period_dtype_code = None
+    del(_period_dtype_code)
     _outputName = "BusinessYearBegin"
     _default_month = 1
     _prefix = "BAS"
@@ -2011,7 +2012,7 @@ cdef class BYearEnd(YearOffset):
     Timestamp('2020-11-30 05:01:15')
     """
 
-    _period_dtype_code = None
+    del(_period_dtype_code)
     _outputName = "BusinessYearEnd"
     _default_month = 12
     _prefix = "BA"
@@ -2030,10 +2031,11 @@ cdef class QuarterOffset(SingleConstructorOffset):
     #       startingMonth vs month attr names are resolved
 
     _attributes = tuple(["n", "normalize", "startingMonth"])
-    _default_month = 1
+    # _default_month = 1
 
     cdef:
         readonly int startingMonth
+        public int _period_dtype_code, _default_month
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
         BaseOffset.__init__(self, n, normalize)
@@ -2170,7 +2172,7 @@ cdef class BQuarterBegin(QuarterOffset):
     Timestamp('2020-08-03 05:01:15')
     """
 
-    _period_dtype_code = None
+    del(_period_dtype_code)
     _output_name = "BusinessQuarterBegin"
     _default_month = 3  # Should be 1
     _from_name_starting_month = 1
@@ -2200,7 +2202,7 @@ cdef class BQuarterEnd(QuarterOffset):
     Timestamp('2020-05-29 05:01:15')
     """
 
-    _period_dtype_code = None
+    del(_period_dtype_code)
     _output_name = "BusinessQuarterEnd"
     _default_month = 3
     _from_name_starting_month = 12

From fdc7e547688cadc4c3cdf62670438d4ed7194d7e Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 22:02:25 +0100
Subject: [PATCH 41/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 146be5538d904..36a121aaeadc5 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1971,7 +1971,7 @@ cdef class BYearBegin(YearOffset):
     Timestamp('2022-01-03 05:01:15')
     """
 
-    del(_period_dtype_code)
+    del _period_dtype_code
     _outputName = "BusinessYearBegin"
     _default_month = 1
     _prefix = "BAS"
@@ -2012,7 +2012,7 @@ cdef class BYearEnd(YearOffset):
     Timestamp('2020-11-30 05:01:15')
     """
 
-    del(_period_dtype_code)
+    del _period_dtype_code
     _outputName = "BusinessYearEnd"
     _default_month = 12
     _prefix = "BA"
@@ -2172,7 +2172,7 @@ cdef class BQuarterBegin(QuarterOffset):
     Timestamp('2020-08-03 05:01:15')
     """
 
-    del(_period_dtype_code)
+    del _period_dtype_code
     _output_name = "BusinessQuarterBegin"
     _default_month = 3  # Should be 1
     _from_name_starting_month = 1
@@ -2202,7 +2202,7 @@ cdef class BQuarterEnd(QuarterOffset):
     Timestamp('2020-05-29 05:01:15')
     """
 
-    del(_period_dtype_code)
+    del _period_dtype_code
     _output_name = "BusinessQuarterEnd"
     _default_month = 3
     _from_name_starting_month = 12

From 070cd72265b94cbeea56efb4a74dde6873d0f079 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 22:34:31 +0100
Subject: [PATCH 42/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 36a121aaeadc5..327768967a9a6 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1971,7 +1971,7 @@ cdef class BYearBegin(YearOffset):
     Timestamp('2022-01-03 05:01:15')
     """
 
-    del _period_dtype_code
+    del self._period_dtype_code
     _outputName = "BusinessYearBegin"
     _default_month = 1
     _prefix = "BAS"
@@ -2012,7 +2012,7 @@ cdef class BYearEnd(YearOffset):
     Timestamp('2020-11-30 05:01:15')
     """
 
-    del _period_dtype_code
+    del self._period_dtype_code
     _outputName = "BusinessYearEnd"
     _default_month = 12
     _prefix = "BA"
@@ -2172,7 +2172,7 @@ cdef class BQuarterBegin(QuarterOffset):
     Timestamp('2020-08-03 05:01:15')
     """
 
-    del _period_dtype_code
+    del self._period_dtype_code
     _output_name = "BusinessQuarterBegin"
     _default_month = 3  # Should be 1
     _from_name_starting_month = 1
@@ -2202,7 +2202,7 @@ cdef class BQuarterEnd(QuarterOffset):
     Timestamp('2020-05-29 05:01:15')
     """
 
-    del _period_dtype_code
+    del self._period_dtype_code
     _output_name = "BusinessQuarterEnd"
     _default_month = 3
     _from_name_starting_month = 12

From efb314ee67b91d4ce0f57ff89c63a475d384f955 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sat, 20 Feb 2021 23:10:09 +0100
Subject: [PATCH 43/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 327768967a9a6..7bb91cabd2d8e 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1971,7 +1971,7 @@ cdef class BYearBegin(YearOffset):
     Timestamp('2022-01-03 05:01:15')
     """
 
-    del self._period_dtype_code
+    del(self._period_dtype_code)
     _outputName = "BusinessYearBegin"
     _default_month = 1
     _prefix = "BAS"
@@ -2012,7 +2012,7 @@ cdef class BYearEnd(YearOffset):
     Timestamp('2020-11-30 05:01:15')
     """
 
-    del self._period_dtype_code
+    del(self._period_dtype_code)
     _outputName = "BusinessYearEnd"
     _default_month = 12
     _prefix = "BA"
@@ -2172,7 +2172,7 @@ cdef class BQuarterBegin(QuarterOffset):
     Timestamp('2020-08-03 05:01:15')
     """
 
-    del self._period_dtype_code
+    del(self._period_dtype_code)
     _output_name = "BusinessQuarterBegin"
     _default_month = 3  # Should be 1
     _from_name_starting_month = 1
@@ -2202,7 +2202,7 @@ cdef class BQuarterEnd(QuarterOffset):
     Timestamp('2020-05-29 05:01:15')
     """
 
-    del self._period_dtype_code
+    del(self._period_dtype_code)
     _output_name = "BusinessQuarterEnd"
     _default_month = 3
     _from_name_starting_month = 12

From 045177eac0b2df15a9860b71d1450ef58ff4e382 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sun, 21 Feb 2021 01:31:33 +0100
Subject: [PATCH 44/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 7bb91cabd2d8e..995435119cf3c 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1971,7 +1971,7 @@ cdef class BYearBegin(YearOffset):
     Timestamp('2022-01-03 05:01:15')
     """
 
-    del(self._period_dtype_code)
+    # del(self._period_dtype_code)
     _outputName = "BusinessYearBegin"
     _default_month = 1
     _prefix = "BAS"
@@ -2012,7 +2012,7 @@ cdef class BYearEnd(YearOffset):
     Timestamp('2020-11-30 05:01:15')
     """
 
-    del(self._period_dtype_code)
+    # del(self._period_dtype_code)
     _outputName = "BusinessYearEnd"
     _default_month = 12
     _prefix = "BA"
@@ -2172,7 +2172,7 @@ cdef class BQuarterBegin(QuarterOffset):
     Timestamp('2020-08-03 05:01:15')
     """
 
-    del(self._period_dtype_code)
+    # del(self._period_dtype_code)
     _output_name = "BusinessQuarterBegin"
     _default_month = 3  # Should be 1
     _from_name_starting_month = 1
@@ -2202,7 +2202,7 @@ cdef class BQuarterEnd(QuarterOffset):
     Timestamp('2020-05-29 05:01:15')
     """
 
-    del(self._period_dtype_code)
+    # del(self._period_dtype_code)
     _output_name = "BusinessQuarterEnd"
     _default_month = 3
     _from_name_starting_month = 12

From 4f15b5bfb1941c735120045870a1d104f4841ee7 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sun, 21 Feb 2021 02:03:41 +0100
Subject: [PATCH 45/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 995435119cf3c..d8f5494c50d1e 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1840,11 +1840,11 @@ cdef class YearOffset(SingleConstructorOffset):
     """
 
     _attributes = tuple(["n", "normalize", "month"])
-    # _default_month = 1
+    _default_month = 1
 
     cdef:
         readonly int month
-        public int _default_month, _period_dtype_code
+        # public int _default_month, _period_dtype_code
 
     def __init__(self, n=1, normalize=False, month=None):
         BaseOffset.__init__(self, n, normalize)
@@ -2031,11 +2031,11 @@ cdef class QuarterOffset(SingleConstructorOffset):
     #       startingMonth vs month attr names are resolved
 
     _attributes = tuple(["n", "normalize", "startingMonth"])
-    # _default_month = 1
+    _default_month = 1
 
     cdef:
         readonly int startingMonth
-        public int _period_dtype_code, _default_month
+        # public int _period_dtype_code, _default_month
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
         BaseOffset.__init__(self, n, normalize)

From fbf3f68c9c75da1c87a6441627fa6c0ed322c881 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sun, 21 Feb 2021 02:24:57 +0100
Subject: [PATCH 46/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index d8f5494c50d1e..441da39f74252 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1843,8 +1843,8 @@ cdef class YearOffset(SingleConstructorOffset):
     _default_month = 1
 
     cdef:
-        readonly int month
-        # public int _default_month, _period_dtype_code
+        readonly int month, _period_dtype_code
+        # public int _period_dtype_code
 
     def __init__(self, n=1, normalize=False, month=None):
         BaseOffset.__init__(self, n, normalize)
@@ -2034,8 +2034,8 @@ cdef class QuarterOffset(SingleConstructorOffset):
     _default_month = 1
 
     cdef:
-        readonly int startingMonth
-        # public int _period_dtype_code, _default_month
+        readonly int startingMonth, _period_dtype_code
+        # public int _period_dtype_code
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
         BaseOffset.__init__(self, n, normalize)

From 5f8711cb72729b83d0604fbdaeffbe736c86828f Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Wed, 17 Mar 2021 22:34:58 +0100
Subject: [PATCH 47/64] Update dtypes.pyx

Add improved "MS" (month start) entry to _period_code_map
---
 pandas/_libs/tslibs/dtypes.pyx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/dtypes.pyx b/pandas/_libs/tslibs/dtypes.pyx
index f36ca20558566..58c1160973137 100644
--- a/pandas/_libs/tslibs/dtypes.pyx
+++ b/pandas/_libs/tslibs/dtypes.pyx
@@ -77,8 +77,8 @@ _period_code_map = {
     "Q-OCT": 2010,    # Quarterly - October year end
     "Q-NOV": 2011,    # Quarterly - November year end
 
-    "M": 3000,        # Monthly
-    "MS": 3000,       # Monthly
+    "M": 3000,        # Monthly - month end
+    "MS": 3001,       # Monthly - month start
 
     "W-SUN": 4000,    # Weekly - Sunday end of week
     "W-MON": 4001,    # Weekly - Monday end of week

From a804a3ed2a768f2bbf9b220352a524109fafc86c Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Mar 2021 00:08:06 +0100
Subject: [PATCH 48/64] Update test_asfreq.py

Parametrize and rename `test_M_vs_MS`, add `MS` tests to `test_asfreq_near_zero`, `test_conv_weekly` and `test_conv_monthly`.
---
 pandas/tests/scalar/period/test_asfreq.py | 36 +++++++++++++++++------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/pandas/tests/scalar/period/test_asfreq.py b/pandas/tests/scalar/period/test_asfreq.py
index c71c5fb613966..36fce1eda354a 100644
--- a/pandas/tests/scalar/period/test_asfreq.py
+++ b/pandas/tests/scalar/period/test_asfreq.py
@@ -13,7 +13,7 @@
 class TestFreqConversion:
     """Test frequency conversion of date objects"""
 
-    @pytest.mark.parametrize("freq", ["A", "Q", "M", "W", "B", "D"])
+    @pytest.mark.parametrize("freq", ["A", "Q", "M", "MS", "W", "B", "D"])
     def test_asfreq_near_zero(self, freq):
         # GH#19643, GH#19650
         per = Period("0001-01-01", freq=freq)
@@ -214,6 +214,7 @@ def test_conv_monthly(self):
         ival_M_to_S_end = Period(
             freq="S", year=2007, month=1, day=31, hour=23, minute=59, second=59
         )
+        ival_MS = Period(freq="MS", year=2007, month=1)
 
         assert ival_M.asfreq("A") == ival_M_to_A
         assert ival_M_end_of_year.asfreq("A") == ival_M_to_A
@@ -234,6 +235,13 @@ def test_conv_monthly(self):
         assert ival_M.asfreq("S", "E") == ival_M_to_S_end
 
         assert ival_M.asfreq("M") == ival_M
+        assert ival_M.asfreq("M") != ival_MS
+        assert ival_M.asfreq("MS") == ival_MS
+        assert ival_M.asfreq("MS") != ival_M
+        assert ival_MS.asfreq("MS") == ival_MS
+        assert ival_MS.asfreq("MS") != ival_M
+        assert ival_MS.asfreq("M") == ival_M
+        assert ival_MS.asfreq("M") != ival_MS
 
     def test_conv_weekly(self):
         # frequency conversion tests: from Weekly Frequency
@@ -268,6 +276,7 @@ def test_conv_weekly(self):
         ival_W_to_A = Period(freq="A", year=2007)
         ival_W_to_Q = Period(freq="Q", year=2007, quarter=1)
         ival_W_to_M = Period(freq="M", year=2007, month=1)
+        ival_W_to_MS = Period(freq="MS", year=2007, month=1)
 
         if Period(freq="D", year=2007, month=12, day=31).weekday == 6:
             ival_W_to_A_end_of_year = Period(freq="A", year=2007)
@@ -310,6 +319,7 @@ def test_conv_weekly(self):
         assert ival_W_end_of_quarter.asfreq("Q") == ival_W_to_Q_end_of_quarter
 
         assert ival_W.asfreq("M") == ival_W_to_M
+        assert ival_W.asfreq("MS") == ival_W_to_MS
         assert ival_W_end_of_month.asfreq("M") == ival_W_to_M_end_of_month
 
         assert ival_W.asfreq("B", "S") == ival_W_to_B_start
@@ -788,13 +798,21 @@ def test_asfreq_combined(self):
         assert result2.ordinal == expected.ordinal
         assert result2.freq == expected.freq
 
-    def test_asfreq_MS(self):
-        initial = Period("2013")
+    @pytest.mark.parametrize(
+        "year_month", ["2013-01", "2021-02", "2022-02", "2020-07", "2027-12"])
+    def test_M_vs_MS(self, year_month):
+        year = year_month.split("-")[0]
+        initial = Period(year)
         ts0 = initial.asfreq(freq="M", how="S").to_timestamp(how="start")
-        ts1 = Period("2013-01", "MS").to_timestamp()
-        ts2 = Period("2013-01", "M").to_timestamp(how="start")
-
-        assert initial.asfreq(freq="M", how="S") == Period("2013-01", "M")
-        assert initial.asfreq(freq="MS", how="S") == Period("2013-01", "MS")
-        assert ts0 == ts1
+        ts1 = Period(year_month, freq="MS").to_timestamp()
+        ts2 = Period(year_month, freq="M").to_timestamp(how="start")
+        ts3 = Period(year_month, freq="M").to_timestamp()
+
+        assert initial.asfreq(freq="M", how="S") == Period(f"{year}-01", "M")
+        assert initial.asfreq(freq="M", how="S") != Period(f"{year}-01", "MS")
+        assert initial.asfreq(freq="MS", how="S") == Period(f"{year}-01", "MS")
+        assert initial.asfreq(freq="MS", how="S") != Period(f"{year}-01", "M")
+        assert initial.asfreq(freq="MS") == Period(f"{year}-12", "MS")
         assert initial.asfreq(freq="MS", how="S").to_timestamp() == ts2
+        assert ts0 == ts1
+        assert ts1 != ts3

From 213fb664e052e777fd05a3f822740ccdad2ac716 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Mar 2021 00:18:37 +0100
Subject: [PATCH 49/64] fix formatting

---
 pandas/tests/scalar/period/test_asfreq.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pandas/tests/scalar/period/test_asfreq.py b/pandas/tests/scalar/period/test_asfreq.py
index 36fce1eda354a..8a15fbd5d938a 100644
--- a/pandas/tests/scalar/period/test_asfreq.py
+++ b/pandas/tests/scalar/period/test_asfreq.py
@@ -799,8 +799,9 @@ def test_asfreq_combined(self):
         assert result2.freq == expected.freq
 
     @pytest.mark.parametrize(
-        "year_month", ["2013-01", "2021-02", "2022-02", "2020-07", "2027-12"])
-    def test_M_vs_MS(self, year_month):
+        "year_month", ["2013-01", "2021-02", "2022-02", "2020-07", "2027-12"]
+    )
+    def test_asfreq_M_vs_MS(self, year_month):
         year = year_month.split("-")[0]
         initial = Period(year)
         ts0 = initial.asfreq(freq="M", how="S").to_timestamp(how="start")

From 50ddb86fa6a40258216dee7c2f53d5dd8ae4b5fe Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 18 Mar 2021 01:11:03 +0100
Subject: [PATCH 50/64] Update test_asfreq.py

Fix test_asfreq_M_vs_MS
---
 pandas/tests/scalar/period/test_asfreq.py | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/pandas/tests/scalar/period/test_asfreq.py b/pandas/tests/scalar/period/test_asfreq.py
index 8a15fbd5d938a..aecb95c5937f6 100644
--- a/pandas/tests/scalar/period/test_asfreq.py
+++ b/pandas/tests/scalar/period/test_asfreq.py
@@ -804,16 +804,13 @@ def test_asfreq_combined(self):
     def test_asfreq_M_vs_MS(self, year_month):
         year = year_month.split("-")[0]
         initial = Period(year)
-        ts0 = initial.asfreq(freq="M", how="S").to_timestamp(how="start")
-        ts1 = Period(year_month, freq="MS").to_timestamp()
-        ts2 = Period(year_month, freq="M").to_timestamp(how="start")
-        ts3 = Period(year_month, freq="M").to_timestamp()
+        ts0 = Period(year_month, freq="MS").to_timestamp()
+        ts1 = Period(year_month, freq="M").to_timestamp()
 
         assert initial.asfreq(freq="M", how="S") == Period(f"{year}-01", "M")
         assert initial.asfreq(freq="M", how="S") != Period(f"{year}-01", "MS")
         assert initial.asfreq(freq="MS", how="S") == Period(f"{year}-01", "MS")
         assert initial.asfreq(freq="MS", how="S") != Period(f"{year}-01", "M")
-        assert initial.asfreq(freq="MS") == Period(f"{year}-12", "MS")
-        assert initial.asfreq(freq="MS", how="S").to_timestamp() == ts2
+        assert initial.asfreq(freq="M", how="E") == Period(f"{year}-12", "M")
+        assert initial.asfreq(freq="MS", how="E") == Period(f"{year}-12", "MS")
         assert ts0 == ts1
-        assert ts1 != ts3

From 2acbd33564f9240f8514ac364417ec1596950dac Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 25 Mar 2021 14:48:45 +0100
Subject: [PATCH 51/64] Fixed "MS" code mapping in _period_code_map

---
 pandas/_libs/tslibs/dtypes.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/dtypes.pyx b/pandas/_libs/tslibs/dtypes.pyx
index 58c1160973137..c611a792f6756 100644
--- a/pandas/_libs/tslibs/dtypes.pyx
+++ b/pandas/_libs/tslibs/dtypes.pyx
@@ -78,7 +78,6 @@ _period_code_map = {
     "Q-NOV": 2011,    # Quarterly - November year end
 
     "M": 3000,        # Monthly - month end
-    "MS": 3001,       # Monthly - month start
 
     "W-SUN": 4000,    # Weekly - Sunday end of week
     "W-MON": 4001,    # Weekly - Monday end of week
@@ -111,6 +110,7 @@ _period_code_map.update({
     "A": 1000,   # Annual
     "W": 4000,   # Weekly
     "C": 5000,   # Custom Business Day
+    "MS": 3000,  # Monthly - beginning of month
 })
 
 cdef set _month_names = {

From 407850c127f517a6996e4a297e69895f2cd1b123 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 25 Mar 2021 21:22:48 +0100
Subject: [PATCH 52/64] Add PeriodDtypeCode to MonthBegin

---
 pandas/_libs/tslibs/offsets.pyx | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 6b35c97e774df..9b47c67cc0e87 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2250,6 +2250,7 @@ cdef class MonthBegin(MonthOffset):
     DateOffset of one month at beginning.
     """
 
+    _period_dtype_code = PeriodDtypeCode.MS
     _prefix = "MS"
     _day_opt = "start"
 

From 7bae3f5aba6be7cda916baa4cb0fad5e6ee5c46c Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 25 Mar 2021 21:46:31 +0100
Subject: [PATCH 53/64] Update offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 276 +++++++++++++-------------------
 1 file changed, 108 insertions(+), 168 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 9b47c67cc0e87..fc7add7858528 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -1838,28 +1838,21 @@ cdef class YearOffset(SingleConstructorOffset):
     """
     DateOffset that just needs a month.
     """
-
     _attributes = tuple(["n", "normalize", "month"])
-    _default_month = 1
 
-    cdef:
-        readonly int month, _period_dtype_code
-        # public int _period_dtype_code
+    # _default_month: int  # FIXME: python annotation here breaks things
+
+    cdef readonly:
+        int month
 
     def __init__(self, n=1, normalize=False, month=None):
         BaseOffset.__init__(self, n, normalize)
 
-        if month is not None:
-            if isinstance(month, str):
-                self.month = MONTH_TO_CAL_NUM[month]
-            elif month >= 1 and month <= 12:
-                self.month = month
-            else:
-                raise ValueError("Month must go from 1 to 12.")
-        else:
-            self.month = self._default_month
+        month = month if month is not None else self._default_month
+        self.month = month
 
-        self._period_dtype_code = PeriodDtypeCode.A + self.month % 12
+        if month < 1 or month > 12:
+            raise ValueError("Month must go from 1 to 12")
 
     cpdef __setstate__(self, state):
         self.month = state.pop("month")
@@ -1872,9 +1865,6 @@ cdef class YearOffset(SingleConstructorOffset):
         kwargs = {}
         if suffix:
             kwargs["month"] = MONTH_TO_CAL_NUM[suffix]
-        else:
-            if cls._default_month is not None:
-                kwargs["month"] = cls._default_month
         return cls(**kwargs)
 
     @property
@@ -1913,44 +1903,30 @@ cdef class YearOffset(SingleConstructorOffset):
         return shifted
 
 
-cdef class YearBegin(YearOffset):
-    """
-    DateOffset increments between calendar year begin dates.
-
-    Examples
-    --------
-    >>> from pandas.tseries.offsets import YearBegin
-    >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + YearBegin()
-    Timestamp('2021-01-01 05:01:15')
-    >>> ts + YearBegin(normalize = True)
-    Timestamp('2021-01-01 00:00:00')
-    """
-
-    _outputName = "YearBegin"
-    _default_month = 1
-    _prefix = "AS"
-    _day_opt = "start"
-
-
-cdef class YearEnd(YearOffset):
+cdef class BYearEnd(YearOffset):
     """
-    DateOffset increments between calendar year ends.
+    DateOffset increments between the last business day of the year.
 
     Examples
     --------
-    >>> from pandas.tseries.offsets import YearEnd
+    >>> from pandas.tseries.offset import BYearEnd
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + YearEnd()
+    >>> ts - BYearEnd()
+    Timestamp('2019-12-31 05:01:15')
+    >>> ts + BYearEnd()
     Timestamp('2020-12-31 05:01:15')
-    >>> ts + YearEnd(normalize = True)
-    Timestamp('2020-12-31 00:00:00')
+    >>> ts + BYearEnd(3)
+    Timestamp('2022-12-30 05:01:15')
+    >>> ts + BYearEnd(-3)
+    Timestamp('2017-12-29 05:01:15')
+    >>> ts + BYearEnd(month=11)
+    Timestamp('2020-11-30 05:01:15')
     """
 
-    _outputName = "YearEnd"
+    _outputName = "BusinessYearEnd"
     _default_month = 12
-    _prefix = "A"
-    _day_opt = "end"
+    _prefix = "BA"
+    _day_opt = "business_end"
 
 
 cdef class BYearBegin(YearOffset):
@@ -1959,7 +1935,7 @@ cdef class BYearBegin(YearOffset):
 
     Examples
     --------
-    >>> from pandas.tseries.offsets import BYearBegin
+    >>> from pandas.tseries.offset import BYearBegin
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
     >>> ts + BYearBegin()
     Timestamp('2021-01-01 05:01:15')
@@ -1971,86 +1947,63 @@ cdef class BYearBegin(YearOffset):
     Timestamp('2022-01-03 05:01:15')
     """
 
-    # del(self._period_dtype_code)
     _outputName = "BusinessYearBegin"
     _default_month = 1
     _prefix = "BAS"
     _day_opt = "business_start"
 
 
-cdef class BYearEnd(YearOffset):
+cdef class YearEnd(YearOffset):
+    """
+    DateOffset increments between calendar year ends.
     """
-    DateOffset increments between the last business days of offset years.
-    Here, the year is a period of 12 consecutive calendar months
-    (January - December by default). The "month" parameter allows custom setting
-    of the final month in a year (and correspondingly - the year start month).
 
-    Parameters
-    ----------
-    n : int, default 1
-        Number of years to offset.
-    normalize : bool, default False
-        If true, the time component of the resulting date-time is converted to
-        00:00:00, i.e. midnight (the start, not the end of date-time).
-    month : int, default 12
-        The calendar month number (12 for December) of the ending month
-        in a custom-defined year to be used as offset.
+    _default_month = 12
+    _prefix = "A"
+    _day_opt = "end"
 
-    Examples
-    --------
-    >>> from pandas.tseries.offsets import BYearEnd
-    >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts - BYearEnd()
-    Timestamp('2019-12-31 05:01:15')
-    >>> ts + BYearEnd()
-    Timestamp('2020-12-31 05:01:15')
-    >>> ts + BYearEnd(3)
-    Timestamp('2022-12-30 05:01:15')
-    >>> ts + BYearEnd(-3)
-    Timestamp('2017-12-29 05:01:15')
-    >>> ts + BYearEnd(month=11)
-    Timestamp('2020-11-30 05:01:15')
+    cdef readonly:
+        int _period_dtype_code
+
+    def __init__(self, n=1, normalize=False, month=None):
+        # Because YearEnd can be the freq for a Period, define its
+        #  _period_dtype_code at construction for performance
+        YearOffset.__init__(self, n, normalize, month)
+        self._period_dtype_code = PeriodDtypeCode.A + self.month % 12
+
+
+cdef class YearBegin(YearOffset):
+    """
+    DateOffset increments between calendar year begin dates.
     """
 
-    # del(self._period_dtype_code)
-    _outputName = "BusinessYearEnd"
-    _default_month = 12
-    _prefix = "BA"
-    _day_opt = "business_end"
+    _default_month = 1
+    _prefix = "AS"
+    _day_opt = "start"
 
 
 # ----------------------------------------------------------------------
 # Quarter-Based Offset Classes
 
 cdef class QuarterOffset(SingleConstructorOffset):
-    """
-    The baseline quarterly DateOffset that just needs a month.
-    """
+    _attributes = tuple(["n", "normalize", "startingMonth"])
     # TODO: Consider combining QuarterOffset and YearOffset __init__ at some
     #       point.  Also apply_index, is_on_offset, rule_code if
     #       startingMonth vs month attr names are resolved
 
-    _attributes = tuple(["n", "normalize", "startingMonth"])
-    _default_month = 1
+    # FIXME: python annotations here breaks things
+    # _default_starting_month: int
+    # _from_name_starting_month: int
 
-    cdef:
-        readonly int startingMonth, _period_dtype_code
-        # public int _period_dtype_code
+    cdef readonly:
+        int startingMonth
 
     def __init__(self, n=1, normalize=False, startingMonth=None):
         BaseOffset.__init__(self, n, normalize)
 
-        if startingMonth is not None:
-            if isinstance(startingMonth, str):
-                self.startingMonth = MONTH_TO_CAL_NUM[startingMonth]
-            elif startingMonth >= 1 and startingMonth <= 12:
-                self.startingMonth = startingMonth
-            else:
-                raise ValueError("Month must go from 1 to 12.")
-        else:
-            self.startingMonth = self._default_month
-
-        self._period_dtype_code = PeriodDtypeCode.Q_DEC + self.startingMonth % 12
+        if startingMonth is None:
+            startingMonth = self._default_starting_month
+        self.startingMonth = startingMonth
 
     cpdef __setstate__(self, state):
         self.startingMonth = state.pop("startingMonth")
@@ -2107,53 +2060,32 @@ cdef class QuarterOffset(SingleConstructorOffset):
         return shifted
 
 
-cdef class QuarterBegin(QuarterOffset):
-    """
-    DateOffset increments between Quarter start dates.
-
-    startingMonth = 1 corresponds to dates like 1/01/2007, 4/01/2007, ...
-    startingMonth = 2 corresponds to dates like 2/01/2007, 5/01/2007, ...
-    startingMonth = 3 corresponds to dates like 3/01/2007, 6/01/2007, ...
-
-    Examples
-    --------
-    >>> from pandas.tseries.offsets import QuarterBegin
-    >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + QuarterBegin(2, startingMonth = 2)
-    Timestamp('2020-11-01 05:01:15')
-    """
-
-    _output_name = "QuarterBegin"
-    _default_month = 3  # should be 1
-    _from_name_starting_month = 1
-    _prefix = "QS"
-    _day_opt = "start"
-
-
-cdef class QuarterEnd(QuarterOffset):
+cdef class BQuarterEnd(QuarterOffset):
     """
-    DateOffset increments between Quarter end dates.
+    DateOffset increments between the last business day of each Quarter.
 
     startingMonth = 1 corresponds to dates like 1/31/2007, 4/30/2007, ...
     startingMonth = 2 corresponds to dates like 2/28/2007, 5/31/2007, ...
-    startingMonth = 3 corresponds to dates like 3/31/2007, 6/30/2007, ...
+    startingMonth = 3 corresponds to dates like 3/30/2007, 6/29/2007, ...
 
     Examples
     --------
-    >>> from pandas.tseries.offsets import QuarterEnd
+    >>> from pandas.tseries.offset import BQuarterEnd
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + QuarterEnd(2)
+    >>> ts + BQuarterEnd()
+    Timestamp('2020-06-30 05:01:15')
+    >>> ts + BQuarterEnd(2)
     Timestamp('2020-09-30 05:01:15')
-    >>> ts + QuarterEnd(1, normalize = True)
-    Timestamp('2020-06-30 00:00:00')
-    >>> ts + QuarterEnd(-2, startingMonth = 2)
-    Timestamp('2019-11-30 05:01:15')
+    >>> ts + BQuarterEnd(1, startingMonth=2)
+    Timestamp('2020-05-29 05:01:15')
+    >>> ts + BQuarterEnd(startingMonth=2)
+    Timestamp('2020-05-29 05:01:15')
     """
-
-    _output_name = "QuarterEnd"
-    _default_month = 3
-    _prefix = "Q"
-    _day_opt = "end"
+    _output_name = "BusinessQuarterEnd"
+    _default_starting_month = 3
+    _from_name_starting_month = 12
+    _prefix = "BQ"
+    _day_opt = "business_end"
 
 
 cdef class BQuarterBegin(QuarterOffset):
@@ -2166,48 +2098,58 @@ cdef class BQuarterBegin(QuarterOffset):
 
     Examples
     --------
-    >>> from pandas.tseries.offsets import BQuarterBegin
+    >>> from pandas.tseries.offset import BQuarterBegin
     >>> ts = pd.Timestamp('2020-05-24 05:01:15')
+    >>> ts + BQuarterBegin()
+    Timestamp('2020-06-01 05:01:15')
+    >>> ts + BQuarterBegin(2)
+    Timestamp('2020-09-01 05:01:15')
     >>> ts + BQuarterBegin(startingMonth=2)
     Timestamp('2020-08-03 05:01:15')
+    >>> ts + BQuarterBegin(-1)
+    Timestamp('2020-03-02 05:01:15')
     """
-
-    # del(self._period_dtype_code)
     _output_name = "BusinessQuarterBegin"
-    _default_month = 3  # Should be 1
+    _default_starting_month = 3
     _from_name_starting_month = 1
     _prefix = "BQS"
     _day_opt = "business_start"
 
 
-cdef class BQuarterEnd(QuarterOffset):
+cdef class QuarterEnd(QuarterOffset):
     """
-    DateOffset increments between the last business day of each Quarter.
+    DateOffset increments between Quarter end dates.
 
     startingMonth = 1 corresponds to dates like 1/31/2007, 4/30/2007, ...
     startingMonth = 2 corresponds to dates like 2/28/2007, 5/31/2007, ...
-    startingMonth = 3 corresponds to dates like 3/30/2007, 6/29/2007, ...
+    startingMonth = 3 corresponds to dates like 3/31/2007, 6/30/2007, ...
+    """
+    _default_starting_month = 3
+    _prefix = "Q"
+    _day_opt = "end"
 
-    Examples
-    --------
-    >>> from pandas.tseries.offsets import BQuarterEnd
-    >>> ts = pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + BQuarterEnd()
-    Timestamp('2020-06-30 05:01:15')
-    >>> ts + BQuarterEnd(2)
-    Timestamp('2020-09-30 05:01:15')
-    >>> ts + BQuarterEnd(1, startingMonth = 2)
-    Timestamp('2020-05-29 05:01:15')
-    >>> ts + BQuarterEnd(startingMonth=2)
-    Timestamp('2020-05-29 05:01:15')
+    cdef readonly:
+        int _period_dtype_code
+
+    def __init__(self, n=1, normalize=False, startingMonth=None):
+        # Because QuarterEnd can be the freq for a Period, define its
+        #  _period_dtype_code at construction for performance
+        QuarterOffset.__init__(self, n, normalize, startingMonth)
+        self._period_dtype_code = PeriodDtypeCode.Q_DEC + self.startingMonth % 12
+
+
+cdef class QuarterBegin(QuarterOffset):
     """
+    DateOffset increments between Quarter start dates.
 
-    # del(self._period_dtype_code)
-    _output_name = "BusinessQuarterEnd"
-    _default_month = 3
-    _from_name_starting_month = 12
-    _prefix = "BQ"
-    _day_opt = "business_end"
+    startingMonth = 1 corresponds to dates like 1/01/2007, 4/01/2007, ...
+    startingMonth = 2 corresponds to dates like 2/01/2007, 5/01/2007, ...
+    startingMonth = 3 corresponds to dates like 3/01/2007, 6/01/2007, ...
+    """
+    _default_starting_month = 3
+    _from_name_starting_month = 1
+    _prefix = "QS"
+    _day_opt = "start"
 
 
 # ----------------------------------------------------------------------
@@ -2280,6 +2222,8 @@ cdef class BusinessMonthBegin(MonthOffset):
     >>> ts + BMonthBegin(-3)
     Timestamp('2020-03-02 05:01:15')
     """
+				  
+					  
 
     _prefix = "BMS"
     _day_opt = "business_start"
@@ -2300,8 +2244,6 @@ cdef class BusinessMonthEnd(MonthOffset):
     >>> ts + BusinessMonthEnd(-2)
     Timestamp('2020-03-31 05:01:15')
     """
-
-    _period_dtype_code = PeriodDtypeCode.M
     _prefix = "BM"
     _day_opt = "business_end"
 
@@ -2321,8 +2263,6 @@ cdef class BusinessMonthBegin(MonthOffset):
     >>> ts + BusinessMonthBegin(-3)
     Timestamp('2020-03-02 05:01:15')
     """
-
-    _period_dtype_code = None
     _prefix = "BMS"
     _day_opt = "business_start"
 

From 1c1fd3a8edb7a59d9d947eb845fce65a6379427e Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 25 Mar 2021 21:56:04 +0100
Subject: [PATCH 54/64] Fix MonthBegin PeriodDtypeCode

---
 pandas/_libs/tslibs/offsets.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index fc7add7858528..f057fc2dbf2d4 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2192,7 +2192,7 @@ cdef class MonthBegin(MonthOffset):
     DateOffset of one month at beginning.
     """
 
-    _period_dtype_code = PeriodDtypeCode.MS
+    _period_dtype_code = PeriodDtypeCode.M
     _prefix = "MS"
     _day_opt = "start"
 

From e519610dc26c4659f89f1a33e6d7563e3efaf873 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 25 Mar 2021 22:29:50 +0100
Subject: [PATCH 55/64] Bug hunt

---
 pandas/_libs/tslibs/offsets.pyx | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index f057fc2dbf2d4..df7205d2d0b19 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2192,7 +2192,7 @@ cdef class MonthBegin(MonthOffset):
     DateOffset of one month at beginning.
     """
 
-    _period_dtype_code = PeriodDtypeCode.M
+    # _period_dtype_code = PeriodDtypeCode.M
     _prefix = "MS"
     _day_opt = "start"
 
@@ -2222,8 +2222,6 @@ cdef class BusinessMonthBegin(MonthOffset):
     >>> ts + BMonthBegin(-3)
     Timestamp('2020-03-02 05:01:15')
     """
-				  
-					  
 
     _prefix = "BMS"
     _day_opt = "business_start"

From c5a69b2d8d7e36908b92b680715d1de99e6effd5 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Thu, 25 Mar 2021 22:38:35 +0100
Subject: [PATCH 56/64] Remove double BusinessMonthBegin

---
 pandas/_libs/tslibs/offsets.pyx | 30 ++++++------------------------
 1 file changed, 6 insertions(+), 24 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index df7205d2d0b19..8de885ee78306 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2192,7 +2192,7 @@ cdef class MonthBegin(MonthOffset):
     DateOffset of one month at beginning.
     """
 
-    # _period_dtype_code = PeriodDtypeCode.M
+    _period_dtype_code = PeriodDtypeCode.M
     _prefix = "MS"
     _day_opt = "start"
 
@@ -2213,13 +2213,13 @@ cdef class BusinessMonthBegin(MonthOffset):
 
     Examples
     --------
-    >>> from pandas.tseries.offset import BMonthBegin
+    >>> from pandas.tseries.offsets import BusinessMonthBegin
     >>> ts=pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + BMonthBegin()
+    >>> ts + BusinessMonthBegin()
     Timestamp('2020-06-01 05:01:15')
-    >>> ts + BMonthBegin(2)
+    >>> ts + BusinessMonthBegin(2)
     Timestamp('2020-07-01 05:01:15')
-    >>> ts + BMonthBegin(-3)
+    >>> ts + BusinessMonthBegin(-3)
     Timestamp('2020-03-02 05:01:15')
     """
 
@@ -2242,29 +2242,11 @@ cdef class BusinessMonthEnd(MonthOffset):
     >>> ts + BusinessMonthEnd(-2)
     Timestamp('2020-03-31 05:01:15')
     """
+
     _prefix = "BM"
     _day_opt = "business_end"
 
 
-cdef class BusinessMonthBegin(MonthOffset):
-    """
-    DateOffset of one month at the first business day.
-
-    Examples
-    --------
-    >>> from pandas.tseries.offsets import BusinessMonthBegin
-    >>> ts=pd.Timestamp('2020-05-24 05:01:15')
-    >>> ts + BusinessMonthBegin()
-    Timestamp('2020-06-01 05:01:15')
-    >>> ts + BusinessMonthBegin(2)
-    Timestamp('2020-07-01 05:01:15')
-    >>> ts + BusinessMonthBegin(-3)
-    Timestamp('2020-03-02 05:01:15')
-    """
-    _prefix = "BMS"
-    _day_opt = "business_start"
-
-
 # ---------------------------------------------------------------------
 # Semi-Month Based Offsets
 

From 0628d22d7fb04b3632a326a7384d11a1ac91fa57 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Tue, 30 Mar 2021 18:07:21 +0200
Subject: [PATCH 57/64] Coverage bug hunt

Alter _period_code_map
---
 pandas/_libs/tslibs/dtypes.pyx | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/dtypes.pyx b/pandas/_libs/tslibs/dtypes.pyx
index c611a792f6756..675a936577cc4 100644
--- a/pandas/_libs/tslibs/dtypes.pyx
+++ b/pandas/_libs/tslibs/dtypes.pyx
@@ -78,6 +78,7 @@ _period_code_map = {
     "Q-NOV": 2011,    # Quarterly - November year end
 
     "M": 3000,        # Monthly - month end
+    "MS": 3000,       # Monthly - beginning of month
 
     "W-SUN": 4000,    # Weekly - Sunday end of week
     "W-MON": 4001,    # Weekly - Monday end of week
@@ -110,7 +111,7 @@ _period_code_map.update({
     "A": 1000,   # Annual
     "W": 4000,   # Weekly
     "C": 5000,   # Custom Business Day
-    "MS": 3000,  # Monthly - beginning of month
+    # "MS": 3000,  # Monthly - beginning of month
 })
 
 cdef set _month_names = {

From ff98362a22e3bf7fffe3c5126c2c264e96b264f9 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Tue, 30 Mar 2021 19:23:52 +0200
Subject: [PATCH 58/64] Revert "Coverage bug hunt"

This reverts commit 0628d22d7fb04b3632a326a7384d11a1ac91fa57.
---
 pandas/_libs/tslibs/dtypes.pyx | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/dtypes.pyx b/pandas/_libs/tslibs/dtypes.pyx
index 675a936577cc4..c611a792f6756 100644
--- a/pandas/_libs/tslibs/dtypes.pyx
+++ b/pandas/_libs/tslibs/dtypes.pyx
@@ -78,7 +78,6 @@ _period_code_map = {
     "Q-NOV": 2011,    # Quarterly - November year end
 
     "M": 3000,        # Monthly - month end
-    "MS": 3000,       # Monthly - beginning of month
 
     "W-SUN": 4000,    # Weekly - Sunday end of week
     "W-MON": 4001,    # Weekly - Monday end of week
@@ -111,7 +110,7 @@ _period_code_map.update({
     "A": 1000,   # Annual
     "W": 4000,   # Weekly
     "C": 5000,   # Custom Business Day
-    # "MS": 3000,  # Monthly - beginning of month
+    "MS": 3000,  # Monthly - beginning of month
 })
 
 cdef set _month_names = {

From 56be0c9efe0679b980e54051d63892e23b6b886d Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Tue, 30 Mar 2021 21:32:13 +0200
Subject: [PATCH 59/64] Bug hunt

---
 pandas/_libs/tslibs/offsets.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 8de885ee78306..39adf98772ec2 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2192,7 +2192,7 @@ cdef class MonthBegin(MonthOffset):
     DateOffset of one month at beginning.
     """
 
-    _period_dtype_code = PeriodDtypeCode.M
+    _period_dtype_code = PeriodDtypeCode.MS
     _prefix = "MS"
     _day_opt = "start"
 

From 5303ff99a70190606c603200bc5008f4d7b8ab42 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Tue, 30 Mar 2021 21:36:41 +0200
Subject: [PATCH 60/64] Revert "Bug hunt"

This reverts commit 56be0c9efe0679b980e54051d63892e23b6b886d.
---
 pandas/_libs/tslibs/offsets.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 39adf98772ec2..8de885ee78306 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -2192,7 +2192,7 @@ cdef class MonthBegin(MonthOffset):
     DateOffset of one month at beginning.
     """
 
-    _period_dtype_code = PeriodDtypeCode.MS
+    _period_dtype_code = PeriodDtypeCode.M
     _prefix = "MS"
     _day_opt = "start"
 

From 8aa0d8f002e308d3b37c801de66cca7965996053 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Fri, 23 Apr 2021 08:59:14 +0200
Subject: [PATCH 61/64] retrigger checks


From cfa29723578ab83ff52fdb0a42a40d885b11da87 Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Fri, 23 Apr 2021 14:20:30 +0200
Subject: [PATCH 62/64] Update v1.3.0.rst

---
 doc/source/whatsnew/v1.3.0.rst | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v1.3.0.rst b/doc/source/whatsnew/v1.3.0.rst
index 1e723493a4cc8..a96b6671dbf65 100644
--- a/doc/source/whatsnew/v1.3.0.rst
+++ b/doc/source/whatsnew/v1.3.0.rst
@@ -145,6 +145,7 @@ Other enhancements
 - :class:`RangeIndex` can now be constructed by passing a ``range`` object directly e.g. ``pd.RangeIndex(range(3))`` (:issue:`12067`)
 - :meth:`round` being enabled for the nullable integer and floating dtypes (:issue:`38844`)
 - :meth:`pandas.read_csv` and :meth:`pandas.read_json` expose the argument ``encoding_errors`` to control how encoding errors are handled (:issue:`39450`)
+- Date offset :class:`MonthBegin` can now be used as a period (:issue:`38859`)
 
 .. ---------------------------------------------------------------------------
 
@@ -632,7 +633,7 @@ I/O
 Period
 ^^^^^^
 - Comparisons of :class:`Period` objects or :class:`Index`, :class:`Series`, or :class:`DataFrame` with mismatched ``PeriodDtype`` now behave like other mismatched-type comparisons, returning ``False`` for equals, ``True`` for not-equal, and raising ``TypeError`` for inequality checks (:issue:`39274`)
--
+- Timestamp.to_period() fails for freq="MS" (:issue:`38914`)
 -
 
 Plotting

From 118f422bb4eae25d1747ef56c24dcbbd02f4439d Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Fri, 23 Apr 2021 14:28:38 +0200
Subject: [PATCH 63/64] Update v1.3.0.rst

---
 doc/source/whatsnew/v1.3.0.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v1.3.0.rst b/doc/source/whatsnew/v1.3.0.rst
index a7ca6c7de3309..cbd3b39a9a0f7 100644
--- a/doc/source/whatsnew/v1.3.0.rst
+++ b/doc/source/whatsnew/v1.3.0.rst
@@ -225,6 +225,7 @@ Other enhancements
 - Constructing a :class:`DataFrame` or :class:`Series` with the ``data`` argument being a Python iterable that is *not* a NumPy ``ndarray`` consisting of NumPy scalars will now result in a dtype with a precision the maximum of the NumPy scalars; this was already the case when ``data`` is a NumPy ``ndarray`` (:issue:`40908`)
 - Add keyword ``sort`` to :func:`pivot_table` to allow non-sorting of the result (:issue:`39143`)
 - Date offset :class:`MonthBegin` can now be used as a period (:issue:`38859`)
+-
 
 .. ---------------------------------------------------------------------------
 

From 8da61dc2e2f360b52f5b754964b066e1f663f03c Mon Sep 17 00:00:00 2001
From: Pawel Kranzberg <pawel@kranzberg.co>
Date: Sun, 25 Apr 2021 17:02:03 +0200
Subject: [PATCH 64/64] retrigger checks