Fixes to resample over DST boundaries. This requires

changes to offset classes that weren't working over
such boundaries as well as adding normalize() on
Timestamp.

Author: rockg

doc/source/whatsnew/v0.16.0.txt

@@ -69,6 +69,7 @@ New features
 - Added ``StringMethods.zfill()`` which behave as the same as standard ``str`` (:issue:`9387`)
 - Added ``days_in_month`` (compatibility alias ``daysinmonth``) property to ``Timestamp``, ``DatetimeIndex``, ``Period``, ``PeriodIndex``, and ``Series.dt`` (:issue:`9572`)
 - Added ``decimal`` option in ``to_csv`` to provide formatting for non-'.' decimal separators (:issue:`781`)
+- Added ``normalize`` option for ``Timestamp`` to normalized to midnight (:issue:`8794`)
 
 .. _whatsnew_0160.enhancements.assign:
 
@@ -463,6 +464,7 @@ Bug Fixes
   To reproduce the old behavior, simply add more precision to the label (e.g., use ``2000-02-01`` instead of ``2000-02``).
 - Bug in adding ``offsets.Nano`` to other offets raises ``TypeError`` (:issue:`9284`)
 - Bug in ``DatetimeIndex`` iteration, related to (:issue:`8890`), fixed in (:issue:`9100`)
+- Bug in ``resample`` around DST transitions (:issue:`5172`, :issue:`8744`, :issue:`8653`, :issue:`9173`, :issue:`9468`).  This required fixing offset classes so they behave correctly on DST transitions.
 - Bug in binary operator method (eg ``.mul()``) alignment with integer levels (:issue:`9463`).
 - Bug in boxplot, scatter and hexbin plot may show an unnecessary warning (:issue:`8877`)
 - Bug in subplot with ``layout`` kw may show unnecessary warning (:issue:`9464`)

pandas/tseries/offsets.py

@@ -54,12 +54,16 @@ def wrapper(self, other):
         nano = getattr(other, 'nanosecond', 0)
 
         try:
-            result = func(self, other)
+            if self._adjust_dst and isinstance(other, Timestamp):
+                other = other.tz_localize(None)
 
-            if self.normalize:
-                # normalize_date returns normal datetime
-                result = tslib.normalize_date(result)
+            result = func(self, other)
+            if self._adjust_dst:
+                result = tslib._localize_pydatetime(result, tz)
+            
             result = Timestamp(result)
+            if self.normalize:
+                result = result.normalize()
 
             # nanosecond may be deleted depending on offset process
             if not self.normalize and nano != 0:
@@ -79,7 +83,7 @@ def wrapper(self, other):
 
             if self.normalize:
                 # normalize_date returns normal datetime
-                result = tslib.normalize_date(result)
+                result = normalize_date(result)
 
             if tz is not None and result.tzinfo is None:
                 result = tslib._localize_pydatetime(result, tz)
@@ -158,6 +162,7 @@ def __add__(date):
         'hour', 'minute', 'second', 'microsecond'
         )
     _use_relativedelta = False
+    _adjust_dst = False
 
     # default for prior pickles
     normalize = False
@@ -380,16 +385,15 @@ def freqstr(self):
 
         return fstr
 
-
 class SingleConstructorOffset(DateOffset):
+    
     @classmethod
     def _from_name(cls, suffix=None):
         # default _from_name calls cls with no args
         if suffix:
             raise ValueError("Bad freq suffix %s" % suffix)
         return cls()
 
-
 class BusinessMixin(object):
     """ mixin to business types to provide related functions """
 
@@ -425,6 +429,7 @@ class BusinessDay(BusinessMixin, SingleConstructorOffset):
     DateOffset subclass representing possibly n business days
     """
     _prefix = 'B'
+    _adjust_dst = True
 
     def __init__(self, n=1, normalize=False, **kwds):
         self.n = int(n)
@@ -685,6 +690,8 @@ def onOffset(self, dt):
 
 
 class MonthOffset(SingleConstructorOffset):
+    _adjust_dst = True
+    
     @property
     def name(self):
         if self.isAnchored:
@@ -925,7 +932,7 @@ class Week(DateOffset):
     weekday : int, default None
         Always generate specific day of week. 0 for Monday
     """
-
+    _adjust_dst = True
     def __init__(self, n=1, normalize=False, **kwds):
         self.n = n
         self.normalize = normalize
@@ -1031,7 +1038,9 @@ class WeekOfMonth(DateOffset):
         5: Saturdays
         6: Sundays
     """
-
+    
+    _adjust_dst = True
+    
     def __init__(self, n=1, normalize=False, **kwds):
         self.n = n
         self.normalize = normalize
@@ -1190,7 +1199,7 @@ class QuarterOffset(DateOffset):
     _default_startingMonth = None
     #: default month in _from_name
     _from_name_startingMonth = None
-
+    _adjust_dst = True
     # TODO: Consider combining QuarterOffset and YearOffset __init__ at some
     #       point
     def __init__(self, n=1, normalize=False, **kwds):
@@ -1395,7 +1404,7 @@ def apply(self, other):
 
 class YearOffset(DateOffset):
     """DateOffset that just needs a month"""
-
+    _adjust_dst = True
     def __init__(self, n=1, normalize=False, **kwds):
         self.month = kwds.get('month', self._default_month)
 
@@ -1627,6 +1636,7 @@ class FY5253(DateOffset):
     _prefix = 'RE'
     _suffix_prefix_last = 'L'
     _suffix_prefix_nearest = 'N'
+    _adjust_dst = True
 
     def __init__(self, n=1, normalize=False, **kwds):
         self.n = n
@@ -1848,6 +1858,7 @@ class FY5253Quarter(DateOffset):
     """
 
     _prefix = 'REQ'
+    _adjust_dst = True
 
     def __init__(self, n=1, normalize=False, **kwds):
         self.n = n
@@ -1966,6 +1977,8 @@ class Easter(DateOffset):
     the revised method which is valid in years
     1583-4099.
     '''
+    _adjust_dst = True
+    
     def __init__(self, n=1, **kwds):
         super(Easter, self).__init__(n, **kwds)
 

pandas/tseries/resample.py

@@ -395,8 +395,8 @@ def _get_range_edges(first, last, offset, closed='left', base=0):
 
     if not isinstance(offset, Tick):  # and first.time() != last.time():
         # hack!
-        first = tools.normalize_date(first)
-        last = tools.normalize_date(last)
+        first = first.normalize()
+        last = last.normalize()
 
     if closed == 'left':
         first = Timestamp(offset.rollback(first))
@@ -409,15 +409,18 @@ def _get_range_edges(first, last, offset, closed='left', base=0):
 
 
 def _adjust_dates_anchored(first, last, offset, closed='right', base=0):
-    from pandas.tseries.tools import normalize_date
+#     from pandas.tseries.tools import normalize_date
 
     # First and last offsets should be calculated from the start day to fix an
     # error cause by resampling across multiple days when a one day period is
     # not a multiple of the frequency.
     #
     # See https://github.com/pydata/pandas/issues/8683
 
-    start_day_nanos = Timestamp(normalize_date(first)).value
+    first_tzinfo = first.tzinfo
+    first = first.tz_localize(None)
+    last = last.tz_localize(None)
+    start_day_nanos = first.normalize().value
 
     base_nanos = (base % offset.n) * offset.nanos // offset.n
     start_day_nanos += base_nanos
@@ -451,8 +454,11 @@ def _adjust_dates_anchored(first, last, offset, closed='right', base=0):
         else:
             lresult = last.value + offset.nanos
 
-    return (Timestamp(fresult, tz=first.tz),
-            Timestamp(lresult, tz=last.tz))
+#     return (Timestamp(fresult, tz=first.tz),
+#             Timestamp(lresult, tz=last.tz))
+
+    return (Timestamp(fresult).tz_localize(first_tzinfo),
+            Timestamp(lresult).tz_localize(first_tzinfo))
 
 
 def asfreq(obj, freq, method=None, how=None, normalize=False):

pandas/tseries/tests/data/dateoffset_0_15_2.pickle

@@ -0,0 +1,187 @@
+(dp0
+S'YearBegin'
+p1
+ccopy_reg
+_reconstructor
+p2
+(cpandas.tseries.offsets
+YearBegin
+p3
+c__builtin__
+object
+p4
+Ntp5
+Rp6
+(dp7
+S'normalize'
+p8
+I00
+sS'kwds'
+p9
+(dp10
+sS'n'
+p11
+I1
+sS'_offset'
+p12
+cdatetime
+timedelta
+p13
+(I1
+I0
+I0
+tp14
+Rp15
+sS'month'
+p16
+I1
+sS'_use_relativedelta'
+p17
+I00
+sbsS'Week'
+p18
+g2
+(cpandas.tseries.offsets
+Week
+p19
+g4
+Ntp20
+Rp21
+(dp22
+g8
+I00
+sS'_inc'
+p23
+g13
+(I7
+I0
+I0
+tp24
+Rp25
+sg9
+(dp26
+sS'weekday'
+p27
+Nsg11
+I1
+sbsS'MonthBegin'
+p28
+g2
+(cpandas.tseries.offsets
+MonthBegin
+p29
+g4
+Ntp30
+Rp31
+(dp32
+g8
+I00
+sg12
+g13
+(I1
+I0
+I0
+tp33
+Rp34
+sg17
+I00
+sg9
+(dp35
+sg11
+I1
+sbsS'Day'
+p36
+g2
+(cpandas.tseries.offsets
+Day
+p37
+g4
+Ntp38
+Rp39
+(dp40
+g8
+I00
+sg12
+g13
+(I1
+I0
+I0
+tp41
+Rp42
+sg17
+I00
+sg9
+(dp43
+sg11
+I1
+sbsS'DateOffset'
+p44
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+(cpandas.tseries.offsets
+DateOffset
+p45
+g4
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+Rp47
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+g8
+I00
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+(cdateutil.relativedelta
+relativedelta
+p49
+g4
+Ntp50
+Rp51
+(dp52
+S'_has_time'
+p53
+I0
+sS'hour'
+p54
+NsS'seconds'
+p55
+I0
+sS'months'
+p56
+I0
+sS'year'
+p57
+NsS'days'
+p58
+I0
+sS'years'
+p59
+I1
+sS'hours'
+p60
+I0
+sS'second'
+p61
+NsS'microsecond'
+p62
+Nsg16
+NsS'microseconds'
+p63
+I0
+sS'leapdays'
+p64
+I0
+sS'minutes'
+p65
+I0
+sS'day'
+p66
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+p67
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+Nsbsg17
+I01
+sg9
+(dp68
+g59
+I1
+ssg11
+I1
+sbs.