From 8fb1a0dc6893de9c914e1b56fa4989fe78918960 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sun, 17 Dec 2017 20:45:42 -0800
Subject: [PATCH 1/8] delegate (most) datetimelike Series arithmetic ops to
 DatetimeIndex

---
 pandas/core/indexes/datetimelike.py           | 15 ++++-
 pandas/core/ops.py                            | 56 +++++++++++++++----
 .../indexes/datetimes/test_arithmetic.py      | 14 +++++
 pandas/tests/series/test_operators.py         | 19 ++++++-
 pandas/tests/series/test_timeseries.py        |  2 +-
 5 files changed, 92 insertions(+), 14 deletions(-)

diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index 8cc996285fbbd..ea3d20c69e3ad 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -11,7 +11,7 @@
 
 import numpy as np
 from pandas.core.dtypes.common import (
-    is_integer, is_float,
+    is_integer, is_float, is_integer_dtype,
     is_bool_dtype, _ensure_int64,
     is_scalar, is_dtype_equal,
     is_list_like, is_timedelta64_dtype)
@@ -650,6 +650,7 @@ def _add_datetimelike_methods(cls):
         def __add__(self, other):
             from pandas.core.index import Index
             from pandas.core.indexes.timedeltas import TimedeltaIndex
+            from pandas.core.indexes.datetimes import DatetimeIndex
             from pandas.tseries.offsets import DateOffset
             if is_timedelta64_dtype(other):
                 return self._add_delta(other)
@@ -664,6 +665,12 @@ def __add__(self, other):
                 return self.shift(other)
             elif isinstance(other, (Index, datetime, np.datetime64)):
                 return self._add_datelike(other)
+            elif (isinstance(self, DatetimeIndex) and
+                  isinstance(other, np.ndarray) and other.size == 1
+                  and is_integer_dtype(other)):
+                # TODO: Should this be allowed if self.freq is not None?
+                raise TypeError("cannot add {cls} and {typ}"
+                                .format(cls=type(cls), typ=type(other)))
             else:  # pragma: no cover
                 return NotImplemented
         cls.__add__ = __add__
@@ -695,6 +702,12 @@ def __sub__(self, other):
                 return self._sub_datelike(other)
             elif isinstance(other, Period):
                 return self._sub_period(other)
+            elif (isinstance(self, DatetimeIndex) and
+                  isinstance(other, np.ndarray) and other.size == 1
+                  and is_integer_dtype(other)):
+                # TODO: Should this be allowed if self.freq is not None?
+                raise TypeError("cannot add {cls} and {typ}"
+                                .format(cls=type(cls), typ=type(other)))
             else:  # pragma: no cover
                 return NotImplemented
         cls.__sub__ = __sub__
diff --git a/pandas/core/ops.py b/pandas/core/ops.py
index 2fb0cbb14c225..689f37bb876a8 100644
--- a/pandas/core/ops.py
+++ b/pandas/core/ops.py
@@ -363,7 +363,7 @@ def __init__(self, left, right, name, na_op):
         rvalues = self._convert_to_array(right, name=name, other=lvalues)
 
         # left
-        self.is_offset_lhs = self._is_offset(left)
+        self.is_offset_lhs = _is_offset(left)
         self.is_timedelta_lhs = is_timedelta64_dtype(lvalues)
         self.is_datetime64_lhs = is_datetime64_dtype(lvalues)
         self.is_datetime64tz_lhs = is_datetime64tz_dtype(lvalues)
@@ -373,7 +373,7 @@ def __init__(self, left, right, name, na_op):
         self.is_floating_lhs = left.dtype.kind == 'f'
 
         # right
-        self.is_offset_rhs = self._is_offset(right)
+        self.is_offset_rhs = _is_offset(right)
         self.is_datetime64_rhs = is_datetime64_dtype(rvalues)
         self.is_datetime64tz_rhs = is_datetime64tz_dtype(rvalues)
         self.is_datetime_rhs = (self.is_datetime64_rhs or
@@ -489,6 +489,7 @@ def _convert_to_array(self, values, name=None, other=None):
             # datetime with tz
             elif (isinstance(ovalues, datetime.datetime) and
                   hasattr(ovalues, 'tzinfo')):
+                # TODO: does this mean to say `ovalues.tzinfo is not None`?
                 values = pd.DatetimeIndex(values)
             # datetime array with tz
             elif is_datetimetz(values):
@@ -515,7 +516,7 @@ def _convert_to_array(self, values, name=None, other=None):
                 values = np.empty(values.shape, dtype=other.dtype)
                 values[:] = iNaT
             return values
-        elif self._is_offset(values):
+        elif _is_offset(values):
             return values
         else:
             raise TypeError("incompatible type [{dtype}] for a "
@@ -618,14 +619,15 @@ def f(x):
 
         return lvalues, rvalues
 
-    def _is_offset(self, arr_or_obj):
-        """ check if obj or all elements of list-like is DateOffset """
-        if isinstance(arr_or_obj, ABCDateOffset):
-            return True
-        elif (is_list_like(arr_or_obj) and len(arr_or_obj) and
-              is_object_dtype(arr_or_obj)):
-            return all(isinstance(x, ABCDateOffset) for x in arr_or_obj)
-        return False
+
+def _is_offset(arr_or_obj):
+    """ check if obj or all elements of list-like is DateOffset """
+    if isinstance(arr_or_obj, ABCDateOffset):
+        return True
+    elif (is_list_like(arr_or_obj) and len(arr_or_obj) and
+          is_object_dtype(arr_or_obj)):
+        return all(isinstance(x, ABCDateOffset) for x in arr_or_obj)
+    return False
 
 
 def _align_method_SERIES(left, right, align_asobject=False):
@@ -663,6 +665,15 @@ def _construct_divmod_result(left, result, index, name, dtype):
     )
 
 
+def _get_series_result_name(left, rvalues):
+    # TODO: Can we just use right instead of rvalues?
+    if isinstance(rvalues, ABCSeries):
+        name = _maybe_match_name(left, rvalues)
+    else:
+        name = left.name
+    return name
+
+
 def _arith_method_SERIES(op, name, str_rep, fill_zeros=None, default_axis=None,
                          construct_result=_construct_result, **eval_kwargs):
     """
@@ -715,6 +726,29 @@ def wrapper(left, right, name=name, na_op=na_op):
         if isinstance(right, ABCDataFrame):
             return NotImplemented
 
+        if _is_offset(right):
+            # special handling for alignment
+            pass
+        elif isinstance(right, pd.PeriodIndex):
+            # not supported for DatetimeIndex
+            pass
+        elif is_datetime64_dtype(left) or is_datetime64tz_dtype(left):
+            # Dispatch to DatetimeIndex method
+            if right is pd.NaT:
+                # DatetimeIndex and Series handle this differently, so
+                # until that is resolved we need to special-case here
+                return construct_result(left, pd.NaT, index=left.index,
+                                        name=left.name, dtype=left.dtype)
+                # TODO: double-check that the tz part of the dtype
+                # is supposed to be retained
+            left, right = _align_method_SERIES(left, right)
+            name = _get_series_result_name(left, right)
+            result = op(pd.DatetimeIndex(left), right)
+            result.name = name  # Needs to be overriden if name is None
+            return construct_result(left, result,
+                                    index=left.index, name=name,
+                                    dtype=result.dtype)
+
         left, right = _align_method_SERIES(left, right)
 
         converted = _Op.get_op(left, right, name, na_op)
diff --git a/pandas/tests/indexes/datetimes/test_arithmetic.py b/pandas/tests/indexes/datetimes/test_arithmetic.py
index a46462e91a866..3b612ef3e1f89 100644
--- a/pandas/tests/indexes/datetimes/test_arithmetic.py
+++ b/pandas/tests/indexes/datetimes/test_arithmetic.py
@@ -363,6 +363,20 @@ def test_datetimeindex_sub_timestamp_overflow(self):
             with pytest.raises(OverflowError):
                 dtimin - variant
 
+    def test_dti_add_intarray(self, tz):
+        rng = pd.date_range('2000-01-01 09:00', freq='H',
+                            periods=10, tz=tz)
+        other = np.array(1, dtype=np.int64)
+        with pytest.raises(TypeError):
+            rng + other
+
+    def test_dti_sub_intarray(self, tz):
+        rng = pd.date_range('2000-01-01 09:00', freq='H',
+                            periods=10, tz=tz)
+        other = np.array(1, dtype=np.int64)
+        with pytest.raises(TypeError):
+            rng - other
+
 
 # GH 10699
 @pytest.mark.parametrize('klass,assert_func', zip([Series, DatetimeIndex],
diff --git a/pandas/tests/series/test_operators.py b/pandas/tests/series/test_operators.py
index 6cc866a35514f..9fc30d3c77164 100644
--- a/pandas/tests/series/test_operators.py
+++ b/pandas/tests/series/test_operators.py
@@ -28,6 +28,23 @@
 from .common import TestData
 
 
+class TestDatetimeLikeArithmetic(object):
+    def test_datetime_sub_datetime_overflow(self):
+        # GH#12534
+        dt = pd.Timestamp('1700-01-31')
+        dti = pd.date_range('1999-09-30', freq='M', periods=10)
+        with pytest.raises(OverflowError):
+            dti - dt
+        with pytest.raises(OverflowError):
+            dt - dti
+
+        ser = pd.Series(dti)
+        with pytest.raises(OverflowError):
+            ser - dt
+        with pytest.raises(OverflowError):
+            dt - ser
+
+
 class TestSeriesOperators(TestData):
 
     def test_series_comparison_scalars(self):
@@ -612,7 +629,7 @@ def run_ops(ops, get_ser, test_ser):
             # defined
             for op_str in ops:
                 op = getattr(get_ser, op_str, None)
-                with tm.assert_raises_regex(TypeError, 'operate'):
+                with tm.assert_raises_regex(TypeError, 'operate|cannot'):
                     op(test_ser)
 
         # ## timedelta64 ###
diff --git a/pandas/tests/series/test_timeseries.py b/pandas/tests/series/test_timeseries.py
index 95410c6ea0105..475b6ace9f7a5 100644
--- a/pandas/tests/series/test_timeseries.py
+++ b/pandas/tests/series/test_timeseries.py
@@ -107,7 +107,7 @@ def test_shift(self):
         # incompat tz
         s2 = Series(date_range('2000-01-01 09:00:00', periods=5,
                                tz='CET'), name='foo')
-        pytest.raises(ValueError, lambda: s - s2)
+        pytest.raises(TypeError, lambda: s - s2)
 
     def test_shift2(self):
         ts = Series(np.random.randn(5),

From 6d7c6fbaf9a5e0871c3738171c582ad421109f9a Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sun, 17 Dec 2017 20:53:05 -0800
Subject: [PATCH 2/8] flake8 fixup

---
 pandas/core/indexes/datetimelike.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index ea3d20c69e3ad..52ad95ae9ab0d 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -666,8 +666,8 @@ def __add__(self, other):
             elif isinstance(other, (Index, datetime, np.datetime64)):
                 return self._add_datelike(other)
             elif (isinstance(self, DatetimeIndex) and
-                  isinstance(other, np.ndarray) and other.size == 1
-                  and is_integer_dtype(other)):
+                  isinstance(other, np.ndarray) and other.size == 1 and
+                  is_integer_dtype(other)):
                 # TODO: Should this be allowed if self.freq is not None?
                 raise TypeError("cannot add {cls} and {typ}"
                                 .format(cls=type(cls), typ=type(other)))
@@ -703,8 +703,8 @@ def __sub__(self, other):
             elif isinstance(other, Period):
                 return self._sub_period(other)
             elif (isinstance(self, DatetimeIndex) and
-                  isinstance(other, np.ndarray) and other.size == 1
-                  and is_integer_dtype(other)):
+                  isinstance(other, np.ndarray) and other.size == 1 and
+                  is_integer_dtype(other)):
                 # TODO: Should this be allowed if self.freq is not None?
                 raise TypeError("cannot add {cls} and {typ}"
                                 .format(cls=type(cls), typ=type(other)))

From d86af39322c804c9476ffecb55762d4c1a74491a Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 18 Dec 2017 07:48:07 -0800
Subject: [PATCH 3/8] move+deprivatize+test is_offset

---
 pandas/core/dtypes/common.py       | 14 ++++++++++++--
 pandas/core/ops.py                 | 23 ++++++-----------------
 pandas/tests/dtypes/test_common.py | 14 ++++++++++++++
 3 files changed, 32 insertions(+), 19 deletions(-)

diff --git a/pandas/core/dtypes/common.py b/pandas/core/dtypes/common.py
index 5b1335c1a834e..5fdc76fe7a4d7 100644
--- a/pandas/core/dtypes/common.py
+++ b/pandas/core/dtypes/common.py
@@ -12,8 +12,8 @@
 from .generic import (ABCCategorical, ABCPeriodIndex,
                       ABCDatetimeIndex, ABCSeries,
                       ABCSparseArray, ABCSparseSeries, ABCCategoricalIndex,
-                      ABCIndexClass)
-from .inference import is_string_like
+                      ABCIndexClass, ABCDateOffset)
+from .inference import is_string_like, is_list_like
 from .inference import *  # noqa
 
 
@@ -266,6 +266,16 @@ def is_datetimetz(arr):
             is_datetime64tz_dtype(arr))
 
 
+def is_offsetlike(arr_or_obj):
+    """ check if obj or all elements of list-like is DateOffset """
+    if isinstance(arr_or_obj, ABCDateOffset):
+        return True
+    elif (is_list_like(arr_or_obj) and len(arr_or_obj) and
+          is_object_dtype(arr_or_obj)):
+        return all(isinstance(x, ABCDateOffset) for x in arr_or_obj)
+    return False
+
+
 def is_period(arr):
     """
     Check whether an array-like is a periodical index.
diff --git a/pandas/core/ops.py b/pandas/core/ops.py
index 689f37bb876a8..d90a367599e73 100644
--- a/pandas/core/ops.py
+++ b/pandas/core/ops.py
@@ -30,7 +30,7 @@
     is_object_dtype, is_timedelta64_dtype,
     is_datetime64_dtype, is_datetime64tz_dtype,
     is_bool_dtype, is_datetimetz,
-    is_list_like,
+    is_list_like, is_offsetlike,
     is_scalar,
     _ensure_object)
 from pandas.core.dtypes.cast import maybe_upcast_putmask, find_common_type
@@ -38,8 +38,7 @@
     ABCSeries,
     ABCDataFrame,
     ABCIndex,
-    ABCPeriodIndex,
-    ABCDateOffset)
+    ABCPeriodIndex)
 
 # -----------------------------------------------------------------------------
 # Functions that add arithmetic methods to objects, given arithmetic factory
@@ -363,7 +362,7 @@ def __init__(self, left, right, name, na_op):
         rvalues = self._convert_to_array(right, name=name, other=lvalues)
 
         # left
-        self.is_offset_lhs = _is_offset(left)
+        self.is_offset_lhs = is_offsetlike(left)
         self.is_timedelta_lhs = is_timedelta64_dtype(lvalues)
         self.is_datetime64_lhs = is_datetime64_dtype(lvalues)
         self.is_datetime64tz_lhs = is_datetime64tz_dtype(lvalues)
@@ -373,7 +372,7 @@ def __init__(self, left, right, name, na_op):
         self.is_floating_lhs = left.dtype.kind == 'f'
 
         # right
-        self.is_offset_rhs = _is_offset(right)
+        self.is_offset_rhs = is_offsetlike(right)
         self.is_datetime64_rhs = is_datetime64_dtype(rvalues)
         self.is_datetime64tz_rhs = is_datetime64tz_dtype(rvalues)
         self.is_datetime_rhs = (self.is_datetime64_rhs or
@@ -516,7 +515,7 @@ def _convert_to_array(self, values, name=None, other=None):
                 values = np.empty(values.shape, dtype=other.dtype)
                 values[:] = iNaT
             return values
-        elif _is_offset(values):
+        elif is_offsetlike(values):
             return values
         else:
             raise TypeError("incompatible type [{dtype}] for a "
@@ -620,16 +619,6 @@ def f(x):
         return lvalues, rvalues
 
 
-def _is_offset(arr_or_obj):
-    """ check if obj or all elements of list-like is DateOffset """
-    if isinstance(arr_or_obj, ABCDateOffset):
-        return True
-    elif (is_list_like(arr_or_obj) and len(arr_or_obj) and
-          is_object_dtype(arr_or_obj)):
-        return all(isinstance(x, ABCDateOffset) for x in arr_or_obj)
-    return False
-
-
 def _align_method_SERIES(left, right, align_asobject=False):
     """ align lhs and rhs Series """
 
@@ -726,7 +715,7 @@ def wrapper(left, right, name=name, na_op=na_op):
         if isinstance(right, ABCDataFrame):
             return NotImplemented
 
-        if _is_offset(right):
+        if is_offsetlike(right):
             # special handling for alignment
             pass
         elif isinstance(right, pd.PeriodIndex):
diff --git a/pandas/tests/dtypes/test_common.py b/pandas/tests/dtypes/test_common.py
index 2146704fea95f..9a18d2d30d0ee 100644
--- a/pandas/tests/dtypes/test_common.py
+++ b/pandas/tests/dtypes/test_common.py
@@ -537,6 +537,20 @@ def test_is_complex_dtype():
     assert com.is_complex_dtype(np.array([1 + 1j, 5]))
 
 
+def test_is_offsetlike():
+    assert com.is_offsetlike(np.array([pd.DateOffset(month=3),
+                                       pd.offsets.Nano()]))
+    assert com.is_offsetlike(pd.offsets.MonthEnd())
+    assert com.is_offsetlike([pd.offsets.MonthBegin(),
+                              pd.offsets.YearBegin()])
+
+    assert not com.is_offsetlike(pd.Timedelta(1))
+    assert not com.isoffsetlike(np.array([1 + 1j, 5]))
+
+    # mixed case
+    assert not com.isoffsetlike([pd.DateOffset(), pd.Timestamp(0)])
+
+
 @pytest.mark.parametrize('input_param,result', [
     (int, np.dtype(int)),
     ('int32', np.dtype('int32')),

From bbea697a39ee93229a338cdb39cd43e260934069 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 18 Dec 2017 09:49:19 -0800
Subject: [PATCH 4/8] fix test

---
 pandas/core/dtypes/common.py       | 23 ++++++++++++++++++++++-
 pandas/tests/dtypes/test_common.py |  5 ++---
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/pandas/core/dtypes/common.py b/pandas/core/dtypes/common.py
index 5fdc76fe7a4d7..e2ee3deb5396e 100644
--- a/pandas/core/dtypes/common.py
+++ b/pandas/core/dtypes/common.py
@@ -267,7 +267,28 @@ def is_datetimetz(arr):
 
 
 def is_offsetlike(arr_or_obj):
-    """ check if obj or all elements of list-like is DateOffset """
+    """
+    Check if obj or all elements of list-like is DateOffset
+
+    Parameters
+    ----------
+    arr_or_obj : object
+
+    Returns
+    -------
+    boolean : Whether the object is a DateOffset or listlike of DatetOffsets
+
+    Examples
+    --------
+    >>> is_offsetlike(pd.DateOffset(days=1))
+    True
+    >>> is_offsetlike('offset')
+    False
+    >>> is_offsetlike([pd.offsets.Minute(4), pd.offsets.MonthEnd()])
+    True
+    >>> is_offsetlike(np.array([pd.DateOffset(months=3), pd.Timestamp.now()]))
+    False
+    """
     if isinstance(arr_or_obj, ABCDateOffset):
         return True
     elif (is_list_like(arr_or_obj) and len(arr_or_obj) and
diff --git a/pandas/tests/dtypes/test_common.py b/pandas/tests/dtypes/test_common.py
index 9a18d2d30d0ee..38eafaabc04e2 100644
--- a/pandas/tests/dtypes/test_common.py
+++ b/pandas/tests/dtypes/test_common.py
@@ -541,14 +541,13 @@ def test_is_offsetlike():
     assert com.is_offsetlike(np.array([pd.DateOffset(month=3),
                                        pd.offsets.Nano()]))
     assert com.is_offsetlike(pd.offsets.MonthEnd())
-    assert com.is_offsetlike([pd.offsets.MonthBegin(),
-                              pd.offsets.YearBegin()])
+    assert com.is_offsetlike(pd.Index([pd.DateOffset(second=1)]))
 
     assert not com.is_offsetlike(pd.Timedelta(1))
     assert not com.isoffsetlike(np.array([1 + 1j, 5]))
 
     # mixed case
-    assert not com.isoffsetlike([pd.DateOffset(), pd.Timestamp(0)])
+    assert not com.isoffsetlike(np.array([pd.DateOffset(), pd.Timestamp(0)]))
 
 
 @pytest.mark.parametrize('input_param,result', [

From 99e6cc6d6fb7e4abe862ab3197720e85babe41ed Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 18 Dec 2017 12:27:25 -0800
Subject: [PATCH 5/8] fixup typo

---
 pandas/tests/dtypes/test_common.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/tests/dtypes/test_common.py b/pandas/tests/dtypes/test_common.py
index 38eafaabc04e2..bfec229d32b22 100644
--- a/pandas/tests/dtypes/test_common.py
+++ b/pandas/tests/dtypes/test_common.py
@@ -544,10 +544,10 @@ def test_is_offsetlike():
     assert com.is_offsetlike(pd.Index([pd.DateOffset(second=1)]))
 
     assert not com.is_offsetlike(pd.Timedelta(1))
-    assert not com.isoffsetlike(np.array([1 + 1j, 5]))
+    assert not com.is_offsetlike(np.array([1 + 1j, 5]))
 
     # mixed case
-    assert not com.isoffsetlike(np.array([pd.DateOffset(), pd.Timestamp(0)]))
+    assert not com.is_offsetlike(np.array([pd.DateOffset(), pd.Timestamp(0)]))
 
 
 @pytest.mark.parametrize('input_param,result', [

From 61f22ba51ab4d95328463f4b1472675d9c264f67 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 18 Dec 2017 15:04:11 -0800
Subject: [PATCH 6/8] Whatsnew note about change in exception class

---
 doc/source/whatsnew/v0.22.0.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v0.22.0.txt b/doc/source/whatsnew/v0.22.0.txt
index dfd222f10d235..96169fcb51aef 100644
--- a/doc/source/whatsnew/v0.22.0.txt
+++ b/doc/source/whatsnew/v0.22.0.txt
@@ -194,6 +194,7 @@ Other API Changes
 - Rearranged the order of keyword arguments in :func:`read_excel()` to align with :func:`read_csv()` (:issue:`16672`)
 - :func:`pandas.merge` now raises a ``ValueError`` when trying to merge on incompatible data types (:issue:`9780`)
 - :func:`wide_to_long` previously kept numeric-like suffixes as ``object`` dtype. Now they are cast to numeric if possible (:issue:`17627`)
+- Subtraction of :class:`DatetimeIndex` with mis-matched timezones will now raise a ``TypeError`` instead of a ``ValueError`` (:issue:`18817`)
 
 .. _whatsnew_0220.deprecations:
 

From cf677a17b856e9b96853a623a636e61ea6fcd088 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 18 Dec 2017 17:34:23 -0800
Subject: [PATCH 7/8] move special case checking inside the is_datetime check

---
 pandas/core/ops.py | 35 +++++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/pandas/core/ops.py b/pandas/core/ops.py
index d90a367599e73..4ae87ab754efc 100644
--- a/pandas/core/ops.py
+++ b/pandas/core/ops.py
@@ -715,14 +715,10 @@ def wrapper(left, right, name=name, na_op=na_op):
         if isinstance(right, ABCDataFrame):
             return NotImplemented
 
-        if is_offsetlike(right):
-            # special handling for alignment
-            pass
-        elif isinstance(right, pd.PeriodIndex):
-            # not supported for DatetimeIndex
-            pass
         elif is_datetime64_dtype(left) or is_datetime64tz_dtype(left):
-            # Dispatch to DatetimeIndex method
+            # Dispatch to DatetimeIndex method; there are a handful of cases
+            # that DatetimeIndex handles differently from Series so we avoid
+            # dispatching.
             if right is pd.NaT:
                 # DatetimeIndex and Series handle this differently, so
                 # until that is resolved we need to special-case here
@@ -730,13 +726,24 @@ def wrapper(left, right, name=name, na_op=na_op):
                                         name=left.name, dtype=left.dtype)
                 # TODO: double-check that the tz part of the dtype
                 # is supposed to be retained
-            left, right = _align_method_SERIES(left, right)
-            name = _get_series_result_name(left, right)
-            result = op(pd.DatetimeIndex(left), right)
-            result.name = name  # Needs to be overriden if name is None
-            return construct_result(left, result,
-                                    index=left.index, name=name,
-                                    dtype=result.dtype)
+            elif is_offsetlike(right):
+                # special handling for alignment
+                pass
+            elif isinstance(right, pd.PeriodIndex):
+                # not supported for DatetimeIndex
+                pass
+            elif (isinstance(other, np.ndarray) and other.size == 1 and
+                  is_integer_dtype(other)):
+                # DatetimeIndex adds this as nanoseconds, needs fixing
+                pass
+            else:
+                left, right = _align_method_SERIES(left, right)
+                name = _get_series_result_name(left, right)
+                result = op(pd.DatetimeIndex(left), right)
+                result.name = name  # Needs to be overriden if name is None
+                return construct_result(left, result,
+                                        index=left.index, name=name,
+                                        dtype=result.dtype)
 
         left, right = _align_method_SERIES(left, right)
 

From ab7501822da0e81424b3568588f0aedff804baf9 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Tue, 19 Dec 2017 08:11:35 -0800
Subject: [PATCH 8/8] fixup name typo

---
 pandas/core/ops.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/core/ops.py b/pandas/core/ops.py
index 49442f0e545ac..30171e3b204ac 100644
--- a/pandas/core/ops.py
+++ b/pandas/core/ops.py
@@ -734,8 +734,8 @@ def wrapper(left, right, name=name, na_op=na_op):
             elif isinstance(right, pd.PeriodIndex):
                 # not supported for DatetimeIndex
                 pass
-            elif (isinstance(other, np.ndarray) and other.size == 1 and
-                  is_integer_dtype(other)):
+            elif (isinstance(right, np.ndarray) and right.size == 1 and
+                  is_integer_dtype(right)):
                 # DatetimeIndex adds this as nanoseconds, needs fixing
                 pass
             else: