From 962604458d91ab0bb5ee1b59247e8b309959f4d6 Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Sat, 12 May 2018 14:07:13 -0700
Subject: [PATCH 01/11] BUG: Localize Index with datetime dtype and integer
 data correctly

---
 pandas/core/indexes/datetimes.py                    | 10 +++++-----
 pandas/tests/indexes/datetimes/test_construction.py |  8 ++++++++
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 9761974d77d4b..8db3e14426308 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -394,10 +394,10 @@ def __new__(cls, data=None,
 
         # data must be Index or np.ndarray here
         if not (is_datetime64_dtype(data) or is_datetimetz(data) or
-                is_integer_dtype(data)):
+                is_integer_dtype(data) or lib.infer_dtype(data) == 'integer'):
             data = tools.to_datetime(data, dayfirst=dayfirst,
                                      yearfirst=yearfirst)
-
+        passed_integer_data = False
         if issubclass(data.dtype.type, np.datetime64) or is_datetimetz(data):
 
             if isinstance(data, DatetimeIndex):
@@ -424,10 +424,9 @@ def __new__(cls, data=None,
                     subarr = data
         else:
             # must be integer dtype otherwise
-            if isinstance(data, Int64Index):
-                raise TypeError('cannot convert Int64Index->DatetimeIndex')
             if data.dtype != _INT64_DTYPE:
                 data = data.astype(np.int64)
+            passed_integer_data = True
             subarr = data.view(_NS_DTYPE)
 
         if isinstance(subarr, DatetimeIndex):
@@ -438,7 +437,8 @@ def __new__(cls, data=None,
                 tz = timezones.maybe_get_tz(tz)
 
                 if (not isinstance(data, DatetimeIndex) or
-                        getattr(data, 'tz', None) is None):
+                        getattr(data, 'tz', None) is None) and
+                    not passed_integer_data:
                     # Convert tz-naive to UTC
                     ints = subarr.view('i8')
                     subarr = conversion.tz_localize_to_utc(ints, tz,
diff --git a/pandas/tests/indexes/datetimes/test_construction.py b/pandas/tests/indexes/datetimes/test_construction.py
index dae69a86910af..4dafb46a64a1a 100644
--- a/pandas/tests/indexes/datetimes/test_construction.py
+++ b/pandas/tests/indexes/datetimes/test_construction.py
@@ -469,6 +469,14 @@ def test_constructor_with_non_normalized_pytz(self, tz):
         result = DatetimeIndex(['2010'], tz=non_norm_tz)
         assert pytz.timezone(tz) is result.tz
 
+    @pytest.mark.parametrize('klass', [Index, DatetimeIndex])
+    @pytest.mark.parametrize('box', [np.array, list])
+    def test_constructor_with_int_tz(self, klass):
+        ts = Timestamp('2018-01-01', tz='US/Pacific')
+        result = klass(box(ts.value), dtype='datetime64[ns, US/Pacific]')
+        expected = klass([ts])
+        tm.assert_index_equal(result, expected)
+
 
 class TestTimeSeries(object):
 

From f5235eb3f8c110231d1ed3074ebe8b81e5e579f0 Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Sun, 13 May 2018 21:32:01 -0700
Subject: [PATCH 02/11] Adjust tests

---
 pandas/core/indexes/datetimes.py                    |  3 +--
 pandas/tests/indexes/datetimes/test_construction.py | 11 +++++------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 8db3e14426308..8594b1d5e176f 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -437,8 +437,7 @@ def __new__(cls, data=None,
                 tz = timezones.maybe_get_tz(tz)
 
                 if (not isinstance(data, DatetimeIndex) or
-                        getattr(data, 'tz', None) is None) and
-                    not passed_integer_data:
+                        getattr(data, 'tz', None) is None) and not passed_integer_data:
                     # Convert tz-naive to UTC
                     ints = subarr.view('i8')
                     subarr = conversion.tz_localize_to_utc(ints, tz,
diff --git a/pandas/tests/indexes/datetimes/test_construction.py b/pandas/tests/indexes/datetimes/test_construction.py
index 4dafb46a64a1a..0fddac4cd22e4 100644
--- a/pandas/tests/indexes/datetimes/test_construction.py
+++ b/pandas/tests/indexes/datetimes/test_construction.py
@@ -33,16 +33,15 @@ def test_construction_with_alt(self):
         tm.assert_index_equal(i, i2)
         assert i.tz.zone == 'US/Eastern'
 
-        i2 = DatetimeIndex(i.tz_localize(None).asi8, tz=i.dtype.tz)
+        i2 = DatetimeIndex(i.asi8, tz=i.dtype.tz)
         tm.assert_index_equal(i, i2)
         assert i.tz.zone == 'US/Eastern'
 
-        i2 = DatetimeIndex(i.tz_localize(None).asi8, dtype=i.dtype)
+        i2 = DatetimeIndex(i.asi8, dtype=i.dtype)
         tm.assert_index_equal(i, i2)
         assert i.tz.zone == 'US/Eastern'
 
-        i2 = DatetimeIndex(
-            i.tz_localize(None).asi8, dtype=i.dtype, tz=i.dtype.tz)
+        i2 = DatetimeIndex(i.asi8, dtype=i.dtype, tz=i.dtype.tz)
         tm.assert_index_equal(i, i2)
         assert i.tz.zone == 'US/Eastern'
 
@@ -471,9 +470,9 @@ def test_constructor_with_non_normalized_pytz(self, tz):
 
     @pytest.mark.parametrize('klass', [Index, DatetimeIndex])
     @pytest.mark.parametrize('box', [np.array, list])
-    def test_constructor_with_int_tz(self, klass):
+    def test_constructor_with_int_tz(self, klass, box):
         ts = Timestamp('2018-01-01', tz='US/Pacific')
-        result = klass(box(ts.value), dtype='datetime64[ns, US/Pacific]')
+        result = klass(box([ts.value]), dtype='datetime64[ns, US/Pacific]')
         expected = klass([ts])
         tm.assert_index_equal(result, expected)
 

From c95ca51fb25a9768d0a347b51ca0152218b5d0cf Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Sat, 19 May 2018 16:38:06 -0700
Subject: [PATCH 03/11] Adjust tests

---
 pandas/core/indexes/datetimes.py | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 9bba7044d6b69..e191a9d0695c6 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -437,7 +437,7 @@ def __new__(cls, data=None,
                 tz = timezones.maybe_get_tz(tz)
 
                 if (not isinstance(data, DatetimeIndex) or
-                        getattr(data, 'tz', None) is None) and not passed_integer_data:
+                    getattr(data, 'tz', None) is None) and not passed_integer_data:
                     # Convert tz-naive to UTC
                     ints = subarr.view('i8')
                     subarr = conversion.tz_localize_to_utc(ints, tz,
@@ -1242,7 +1242,7 @@ def join(self, other, how='left', level=None, return_indexers=False,
         See Index.join
         """
         if (not isinstance(other, DatetimeIndex) and len(other) > 0 and
-            other.inferred_type not in ('floating', 'mixed-integer',
+            other.inferred_type not in ('floating', 'integer', 'mixed-integer',
                                         'mixed-integer-float', 'mixed')):
             try:
                 other = DatetimeIndex(other)
@@ -2080,8 +2080,9 @@ def normalize(self):
                        dtype='datetime64[ns, Asia/Calcutta]', freq=None)
         """
         new_values = conversion.date_normalize(self.asi8, self.tz)
-        return DatetimeIndex(new_values, freq='infer', name=self.name,
-                             tz=self.tz)
+        return DatetimeIndex(new_values,
+                             freq='infer',
+                             name=self.name).tz_localize(self.tz)
 
     @Substitution(klass='DatetimeIndex')
     @Appender(_shared_docs['searchsorted'])
@@ -2162,8 +2163,6 @@ def insert(self, loc, item):
         try:
             new_dates = np.concatenate((self[:loc].asi8, [item.view(np.int64)],
                                         self[loc:].asi8))
-            if self.tz is not None:
-                new_dates = conversion.tz_convert(new_dates, 'UTC', self.tz)
             return DatetimeIndex(new_dates, name=self.name, freq=freq,
                                  tz=self.tz)
         except (AttributeError, TypeError):
@@ -2201,8 +2200,6 @@ def delete(self, loc):
                 if (loc.start in (0, None) or loc.stop in (len(self), None)):
                     freq = self.freq
 
-        if self.tz is not None:
-            new_dates = conversion.tz_convert(new_dates, 'UTC', self.tz)
         return DatetimeIndex(new_dates, name=self.name, freq=freq, tz=self.tz)
 
     def tz_convert(self, tz):

From cc687644fd13613330fd19d79698a196d5a6eeec Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Sun, 20 May 2018 09:31:18 -0700
Subject: [PATCH 04/11] Refactor processing logic

---
 pandas/core/indexes/datetimes.py | 69 +++++++++++++-------------------
 pandas/io/formats/format.py      |  6 ++-
 2 files changed, 32 insertions(+), 43 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index e191a9d0695c6..330644beab906 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -397,53 +397,40 @@ def __new__(cls, data=None,
                 is_integer_dtype(data) or lib.infer_dtype(data) == 'integer'):
             data = tools.to_datetime(data, dayfirst=dayfirst,
                                      yearfirst=yearfirst)
-        passed_integer_data = False
-        if issubclass(data.dtype.type, np.datetime64) or is_datetimetz(data):
-
-            if isinstance(data, DatetimeIndex):
-                if tz is None:
-                    tz = data.tz
-                elif data.tz is None:
-                    data = data.tz_localize(tz, ambiguous=ambiguous)
-                else:
-                    # the tz's must match
-                    if str(tz) != str(data.tz):
-                        msg = ('data is already tz-aware {0}, unable to '
-                               'set specified tz: {1}')
-                        raise TypeError(msg.format(data.tz, tz))
+        import pdb; pdb.set_trace()
+        if isinstance(data, DatetimeIndex):
+            if tz is None:
+                tz = data.tz
+            elif data.tz is None:
+                data = data.tz_localize(tz, ambiguous=ambiguous)
+            else:
+                # the tz's must match
+                if str(tz) != str(data.tz):
+                    msg = ('data is already tz-aware {0}, unable to '
+                           'set specified tz: {1}')
+                    raise TypeError(msg.format(data.tz, tz))
 
-                subarr = data.values
+            subarr = data.values
 
-                if freq is None:
-                    freq = data.freq
-                    verify_integrity = False
-            else:
-                if data.dtype != _NS_DTYPE:
-                    subarr = conversion.ensure_datetime64ns(data)
-                else:
-                    subarr = data
+            if freq is None:
+                freq = data.freq
+                verify_integrity = False
+        elif issubclass(data.dtype.type, np.datetime64):
+            if data.dtype != _NS_DTYPE:
+                data = conversion.ensure_datetime64ns(data)
+            if tz is not None:
+                # Convert tz-naive to UTC
+                tz = timezones.maybe_get_tz(tz)
+                data = conversion.tz_localize_to_utc(data.view('i8'), tz,
+                                                     ambiguous=ambiguous)
+            subarr = data.view(_NS_DTYPE)
         else:
             # must be integer dtype otherwise
+            # assume this data are epoch timestamps
             if data.dtype != _INT64_DTYPE:
                 data = data.astype(np.int64)
-            passed_integer_data = True
             subarr = data.view(_NS_DTYPE)
 
-        if isinstance(subarr, DatetimeIndex):
-            if tz is None:
-                tz = subarr.tz
-        else:
-            if tz is not None:
-                tz = timezones.maybe_get_tz(tz)
-
-                if (not isinstance(data, DatetimeIndex) or
-                    getattr(data, 'tz', None) is None) and not passed_integer_data:
-                    # Convert tz-naive to UTC
-                    ints = subarr.view('i8')
-                    subarr = conversion.tz_localize_to_utc(ints, tz,
-                                                           ambiguous=ambiguous)
-                subarr = subarr.view(_NS_DTYPE)
-
         subarr = cls._simple_new(subarr, name=name, freq=freq, tz=tz)
         if dtype is not None:
             if not is_dtype_equal(subarr.dtype, dtype):
@@ -630,7 +617,7 @@ def _simple_new(cls, values, name=None, freq=None, tz=None,
         we require the we have a dtype compat for the values
         if we are passed a non-dtype compat, then coerce using the constructor
         """
-
+        import pdb; pdb.set_trace()
         if getattr(values, 'dtype', None) is None:
             # empty, but with dtype compat
             if values is None:
@@ -806,7 +793,7 @@ def _mpl_repr(self):
     @cache_readonly
     def _is_dates_only(self):
         from pandas.io.formats.format import _is_dates_only
-        return _is_dates_only(self.values)
+        return _is_dates_only(self.values) and self.tz is None
 
     @property
     def _formatter_func(self):
diff --git a/pandas/io/formats/format.py b/pandas/io/formats/format.py
index 12201f62946ac..e03a1e98311e2 100644
--- a/pandas/io/formats/format.py
+++ b/pandas/io/formats/format.py
@@ -1237,6 +1237,7 @@ def format_percentiles(percentiles):
 
 
 def _is_dates_only(values):
+    import pdb; pdb.set_trace()
     # return a boolean if we are only dates (and don't have a timezone)
     values = DatetimeIndex(values)
     if values.tz is not None:
@@ -1253,6 +1254,7 @@ def _is_dates_only(values):
 
 
 def _format_datetime64(x, tz=None, nat_rep='NaT'):
+    import pdb; pdb.set_trace()
     if x is None or (is_scalar(x) and isna(x)):
         return nat_rep
 
@@ -1276,7 +1278,7 @@ def _format_datetime64_dateonly(x, nat_rep='NaT', date_format=None):
 
 
 def _get_format_datetime64(is_dates_only, nat_rep='NaT', date_format=None):
-
+    import pdb; pdb.set_trace()
     if is_dates_only:
         return lambda x, tz=None: _format_datetime64_dateonly(
             x, nat_rep=nat_rep, date_format=date_format)
@@ -1296,7 +1298,7 @@ class Datetime64TZFormatter(Datetime64Formatter):
 
     def _format_strings(self):
         """ we by definition have a TZ """
-
+        import pdb; pdb.set_trace()
         values = self.values.astype(object)
         is_dates_only = _is_dates_only(values)
         formatter = (self.formatter or

From 86a40a147867485b797ee739831d27ad80a006db Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Mon, 21 May 2018 22:39:09 -0700
Subject: [PATCH 05/11] Adjust test

---
 pandas/core/indexes/datetimes.py  |  3 +--
 pandas/io/formats/format.py       |  8 ++++----
 pandas/tests/indexes/test_base.py | 24 ++++++++++++++----------
 3 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 330644beab906..02be4b0c80041 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -397,7 +397,7 @@ def __new__(cls, data=None,
                 is_integer_dtype(data) or lib.infer_dtype(data) == 'integer'):
             data = tools.to_datetime(data, dayfirst=dayfirst,
                                      yearfirst=yearfirst)
-        import pdb; pdb.set_trace()
+
         if isinstance(data, DatetimeIndex):
             if tz is None:
                 tz = data.tz
@@ -617,7 +617,6 @@ def _simple_new(cls, values, name=None, freq=None, tz=None,
         we require the we have a dtype compat for the values
         if we are passed a non-dtype compat, then coerce using the constructor
         """
-        import pdb; pdb.set_trace()
         if getattr(values, 'dtype', None) is None:
             # empty, but with dtype compat
             if values is None:
diff --git a/pandas/io/formats/format.py b/pandas/io/formats/format.py
index e03a1e98311e2..fee63957a9397 100644
--- a/pandas/io/formats/format.py
+++ b/pandas/io/formats/format.py
@@ -1237,7 +1237,7 @@ def format_percentiles(percentiles):
 
 
 def _is_dates_only(values):
-    import pdb; pdb.set_trace()
+
     # return a boolean if we are only dates (and don't have a timezone)
     values = DatetimeIndex(values)
     if values.tz is not None:
@@ -1254,7 +1254,7 @@ def _is_dates_only(values):
 
 
 def _format_datetime64(x, tz=None, nat_rep='NaT'):
-    import pdb; pdb.set_trace()
+
     if x is None or (is_scalar(x) and isna(x)):
         return nat_rep
 
@@ -1278,7 +1278,7 @@ def _format_datetime64_dateonly(x, nat_rep='NaT', date_format=None):
 
 
 def _get_format_datetime64(is_dates_only, nat_rep='NaT', date_format=None):
-    import pdb; pdb.set_trace()
+
     if is_dates_only:
         return lambda x, tz=None: _format_datetime64_dateonly(
             x, nat_rep=nat_rep, date_format=date_format)
@@ -1298,7 +1298,7 @@ class Datetime64TZFormatter(Datetime64Formatter):
 
     def _format_strings(self):
         """ we by definition have a TZ """
-        import pdb; pdb.set_trace()
+
         values = self.values.astype(object)
         is_dates_only = _is_dates_only(values)
         formatter = (self.formatter or
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index f9f16dc0ce8b7..9730c224e18e2 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -402,26 +402,30 @@ def test_constructor_dtypes_to_timedelta(self, cast_index, vals):
             index = Index(vals)
             assert isinstance(index, TimedeltaIndex)
 
-    @pytest.mark.parametrize("values", [
-        # pass values without timezone, as DatetimeIndex localizes it
-        pd.date_range('2011-01-01', periods=5).values,
-        pd.date_range('2011-01-01', periods=5).asi8])
+    @pytest.mark.parametrize("attr, utc", [
+        ['values', False],
+        ['asi8', True]])
     @pytest.mark.parametrize("klass", [pd.Index, pd.DatetimeIndex])
-    def test_constructor_dtypes_datetime(self, tz_naive_fixture, values,
+    def test_constructor_dtypes_datetime(self, tz_naive_fixture, attr, utc,
                                          klass):
-        index = pd.date_range('2011-01-01', periods=5, tz=tz_naive_fixture)
+        index = pd.date_range('2011-01-01', periods=5)
+        arg = getattr(index, attr)
+        if utc:
+            index = index.tz_localize('UTC').tz_convert(tz_naive_fixture)
+        else:
+            index = index.tz_localize(tz_naive_fixture)
         dtype = index.dtype
 
-        result = klass(values, tz=tz_naive_fixture)
+        result = klass(arg, tz=tz_naive_fixture)
         tm.assert_index_equal(result, index)
 
-        result = klass(values, dtype=dtype)
+        result = klass(arg, dtype=dtype)
         tm.assert_index_equal(result, index)
 
-        result = klass(list(values), tz=tz_naive_fixture)
+        result = klass(list(arg), tz=tz_naive_fixture)
         tm.assert_index_equal(result, index)
 
-        result = klass(list(values), dtype=dtype)
+        result = klass(list(arg), dtype=dtype)
         tm.assert_index_equal(result, index)
 
     @pytest.mark.parametrize("attr", ['values', 'asi8'])

From 74661ca2734f72028ebb21fc797397ec6f399398 Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Wed, 23 May 2018 11:41:14 -0700
Subject: [PATCH 06/11] add additional comment

---
 pandas/core/indexes/datetimes.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 02be4b0c80041..6df495fe252c8 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -791,6 +791,7 @@ def _mpl_repr(self):
 
     @cache_readonly
     def _is_dates_only(self):
+        """Return a boolean if we are only dates (and don't have a timezone)"""
         from pandas.io.formats.format import _is_dates_only
         return _is_dates_only(self.values) and self.tz is None
 

From abf3efc8e4020e39b93b920132b583bddea052a8 Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Fri, 25 May 2018 22:25:52 -0700
Subject: [PATCH 07/11] adjust blank spaces

---
 pandas/core/indexes/datetimes.py | 1 +
 pandas/io/formats/format.py      | 2 --
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 6df495fe252c8..f3ef18c89174d 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -617,6 +617,7 @@ def _simple_new(cls, values, name=None, freq=None, tz=None,
         we require the we have a dtype compat for the values
         if we are passed a non-dtype compat, then coerce using the constructor
         """
+
         if getattr(values, 'dtype', None) is None:
             # empty, but with dtype compat
             if values is None:
diff --git a/pandas/io/formats/format.py b/pandas/io/formats/format.py
index fee63957a9397..12201f62946ac 100644
--- a/pandas/io/formats/format.py
+++ b/pandas/io/formats/format.py
@@ -1237,7 +1237,6 @@ def format_percentiles(percentiles):
 
 
 def _is_dates_only(values):
-
     # return a boolean if we are only dates (and don't have a timezone)
     values = DatetimeIndex(values)
     if values.tz is not None:
@@ -1254,7 +1253,6 @@ def _is_dates_only(values):
 
 
 def _format_datetime64(x, tz=None, nat_rep='NaT'):
-
     if x is None or (is_scalar(x) and isna(x)):
         return nat_rep
 

From ec4795b72b2f7cb72a364cdf35404d0b3ccd901a Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Tue, 29 May 2018 23:24:39 -0700
Subject: [PATCH 08/11] Address review

---
 doc/source/whatsnew/v0.24.0.txt               |  4 +-
 pandas/core/indexes/base.py                   |  4 ++
 pandas/tests/indexes/datetimes/test_astype.py |  7 +++
 .../indexes/datetimes/test_construction.py    | 44 +++++++++++--------
 pandas/tests/indexes/test_base.py             |  3 ++
 5 files changed, 41 insertions(+), 21 deletions(-)

diff --git a/doc/source/whatsnew/v0.24.0.txt b/doc/source/whatsnew/v0.24.0.txt
index e931450cb5c01..2dee2048eb842 100644
--- a/doc/source/whatsnew/v0.24.0.txt
+++ b/doc/source/whatsnew/v0.24.0.txt
@@ -34,7 +34,7 @@ Datetimelike API Changes
 Other API Changes
 ^^^^^^^^^^^^^^^^^
 
--
+- :class:`DatetimeIndex` now accepts :class:`Int64Index` arguments as epoch timestamps (:issue:`20997`)
 -
 -
 
@@ -90,7 +90,7 @@ Categorical
 Datetimelike
 ^^^^^^^^^^^^
 
--
+- Bug in :class:`Index` with ``datetime64[ns, tz]`` dtype that did not localize integer data correctly (:issue:`20964`)
 -
 -
 
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 229624c7e6645..dc4644157592d 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -1163,6 +1163,10 @@ def astype(self, dtype, copy=True):
             from .category import CategoricalIndex
             return CategoricalIndex(self.values, name=self.name, dtype=dtype,
                                     copy=copy)
+        elif is_datetime64tz_dtype(dtype):
+            from pandas.core.indexes.datetimes import DatetimeIndex
+            return DatetimeIndex(self.values, name=self.name, dtype=dtype,
+                                 copy=copy)
         try:
             return Index(self.values.astype(dtype, copy=copy), name=self.name,
                          dtype=dtype)
diff --git a/pandas/tests/indexes/datetimes/test_astype.py b/pandas/tests/indexes/datetimes/test_astype.py
index 8acdd301f241a..2b22938d8a1ac 100644
--- a/pandas/tests/indexes/datetimes/test_astype.py
+++ b/pandas/tests/indexes/datetimes/test_astype.py
@@ -225,6 +225,13 @@ def _check_rng(rng):
         _check_rng(rng_eastern)
         _check_rng(rng_utc)
 
+    def test_integer_index_astype_datetimetz_dtype(self):
+        # GH 20997, 20964
+        val = [pd.Timestamp('2018-01-01', tz='US/Pacific').value]
+        result = pd.Index(val).astype('datetime64[ns, US/Pacific]')
+        expected = pd.DatetimeIndex(['2018-01-01'], tz='US/Pacific')
+        tm.assert_index_equal(result, expected)
+
 
 class TestToPeriod(object):
 
diff --git a/pandas/tests/indexes/datetimes/test_construction.py b/pandas/tests/indexes/datetimes/test_construction.py
index 0fddac4cd22e4..bfc964634ee13 100644
--- a/pandas/tests/indexes/datetimes/test_construction.py
+++ b/pandas/tests/indexes/datetimes/test_construction.py
@@ -1,8 +1,9 @@
-import pytest
+from datetime import timedelta
+from operator import attrgetter
 
+import pytest
 import pytz
 import numpy as np
-from datetime import timedelta
 
 import pandas as pd
 from pandas import offsets
@@ -26,24 +27,28 @@ def test_construction_caching(self):
                                                  freq='ns')})
         assert df.dttz.dtype.tz.zone == 'US/Eastern'
 
-    def test_construction_with_alt(self):
-
+    @pytest.mark.parametrize('kwargs', [
+        {'tz': 'dtype.tz'},
+        {'dtype': 'dtype'},
+        {'dtype': 'dtype', 'tz': 'dtype.tz'}])
+    def test_construction_with_alt(self, kwargs):
         i = pd.date_range('20130101', periods=5, freq='H', tz='US/Eastern')
-        i2 = DatetimeIndex(i, dtype=i.dtype)
-        tm.assert_index_equal(i, i2)
-        assert i.tz.zone == 'US/Eastern'
-
-        i2 = DatetimeIndex(i.asi8, tz=i.dtype.tz)
-        tm.assert_index_equal(i, i2)
-        assert i.tz.zone == 'US/Eastern'
-
-        i2 = DatetimeIndex(i.asi8, dtype=i.dtype)
-        tm.assert_index_equal(i, i2)
-        assert i.tz.zone == 'US/Eastern'
-
-        i2 = DatetimeIndex(i.asi8, dtype=i.dtype, tz=i.dtype.tz)
-        tm.assert_index_equal(i, i2)
-        assert i.tz.zone == 'US/Eastern'
+        kwargs = {key: attrgetter(val)(i) for key, val in kwargs.items()}
+        result = DatetimeIndex(i, **kwargs)
+        tm.assert_index_equal(i, result)
+        assert result.tz.zone == 'US/Eastern'
+
+    @pytest.mark.parametrize('kwargs', [
+        {'tz': 'dtype.tz'},
+        {'dtype': 'dtype'},
+        {'dtype': 'dtype', 'tz': 'dtype.tz'}])
+    def test_construction_with_alt_tz_localize(self, kwargs):
+        i = pd.date_range('20130101', periods=5, freq='H', tz='US/Eastern')
+        kwargs = {key: attrgetter(val)(i) for key, val in kwargs.items()}
+        result = DatetimeIndex(i.tz_localize(None).asi8, **kwargs)
+        expected = i - pd.Timedelta(hours=5)
+        tm.assert_index_equal(result, expected)
+        assert result.tz.zone == 'US/Eastern'
 
         # localize into the provided tz
         i2 = DatetimeIndex(i.tz_localize(None).asi8, tz='UTC')
@@ -471,6 +476,7 @@ def test_constructor_with_non_normalized_pytz(self, tz):
     @pytest.mark.parametrize('klass', [Index, DatetimeIndex])
     @pytest.mark.parametrize('box', [np.array, list])
     def test_constructor_with_int_tz(self, klass, box):
+        # GH 20997, 20964
         ts = Timestamp('2018-01-01', tz='US/Pacific')
         result = klass(box([ts.value]), dtype='datetime64[ns, US/Pacific]')
         expected = klass([ts])
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index 9730c224e18e2..dc1c70bd5bc44 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -408,6 +408,9 @@ def test_constructor_dtypes_to_timedelta(self, cast_index, vals):
     @pytest.mark.parametrize("klass", [pd.Index, pd.DatetimeIndex])
     def test_constructor_dtypes_datetime(self, tz_naive_fixture, attr, utc,
                                          klass):
+        # Test constructing with a datetimetz dtype
+        # .values produces numpy datetimes, so these are considered naive
+        # .asi8 produces integers, so these are considered epoch timestamps
         index = pd.date_range('2011-01-01', periods=5)
         arg = getattr(index, attr)
         if utc:

From 37484eaeab309050fa0fa23cd8312023c7a7117e Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Sat, 2 Jun 2018 13:42:05 -0700
Subject: [PATCH 09/11] Adjust astype

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

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index dc4644157592d..d3ed0f7b8ae55 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -1163,11 +1163,11 @@ def astype(self, dtype, copy=True):
             from .category import CategoricalIndex
             return CategoricalIndex(self.values, name=self.name, dtype=dtype,
                                     copy=copy)
-        elif is_datetime64tz_dtype(dtype):
-            from pandas.core.indexes.datetimes import DatetimeIndex
-            return DatetimeIndex(self.values, name=self.name, dtype=dtype,
-                                 copy=copy)
         try:
+            if is_datetime64tz_dtype(dtype):
+                from pandas.core.indexes.datetimes import DatetimeIndex
+                return DatetimeIndex(self.values, name=self.name, dtype=dtype,
+                                     copy=copy)
             return Index(self.values.astype(dtype, copy=copy), name=self.name,
                          dtype=dtype)
         except (TypeError, ValueError):

From dc0a3fe834a73af7ca8b00f450b14be467299b1f Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Wed, 6 Jun 2018 18:08:26 -0700
Subject: [PATCH 10/11] Add fixture tests, test with object data, dont copy
 with astype

---
 pandas/core/indexes/datetimes.py              |  2 +-
 pandas/tests/indexes/datetimes/test_astype.py | 11 +++++---
 .../indexes/datetimes/test_construction.py    | 27 +++++++++++--------
 3 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index f3ef18c89174d..35f6e751caa6c 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -428,7 +428,7 @@ def __new__(cls, data=None,
             # must be integer dtype otherwise
             # assume this data are epoch timestamps
             if data.dtype != _INT64_DTYPE:
-                data = data.astype(np.int64)
+                data = data.astype(np.int64, copy=False)
             subarr = data.view(_NS_DTYPE)
 
         subarr = cls._simple_new(subarr, name=name, freq=freq, tz=tz)
diff --git a/pandas/tests/indexes/datetimes/test_astype.py b/pandas/tests/indexes/datetimes/test_astype.py
index 2b22938d8a1ac..64b8f48f6a4e1 100644
--- a/pandas/tests/indexes/datetimes/test_astype.py
+++ b/pandas/tests/indexes/datetimes/test_astype.py
@@ -225,11 +225,14 @@ def _check_rng(rng):
         _check_rng(rng_eastern)
         _check_rng(rng_utc)
 
-    def test_integer_index_astype_datetimetz_dtype(self):
+    @pytest.mark.parametrize('tz, dtype', [
+        ['US/Pacific', 'datetime64[ns, US/Pacific]'],
+        [None, 'datetime64[ns]']])
+    def test_integer_index_astype_datetime(self, tz, dtype):
         # GH 20997, 20964
-        val = [pd.Timestamp('2018-01-01', tz='US/Pacific').value]
-        result = pd.Index(val).astype('datetime64[ns, US/Pacific]')
-        expected = pd.DatetimeIndex(['2018-01-01'], tz='US/Pacific')
+        val = [pd.Timestamp('2018-01-01', tz=tz).value]
+        result = pd.Index(val).astype(dtype)
+        expected = pd.DatetimeIndex(['2018-01-01'], tz=tz)
         tm.assert_index_equal(result, expected)
 
 
diff --git a/pandas/tests/indexes/datetimes/test_construction.py b/pandas/tests/indexes/datetimes/test_construction.py
index bfc964634ee13..360cc42afc1c4 100644
--- a/pandas/tests/indexes/datetimes/test_construction.py
+++ b/pandas/tests/indexes/datetimes/test_construction.py
@@ -1,5 +1,6 @@
 from datetime import timedelta
 from operator import attrgetter
+from functools import partial
 
 import pytest
 import pytz
@@ -31,24 +32,24 @@ def test_construction_caching(self):
         {'tz': 'dtype.tz'},
         {'dtype': 'dtype'},
         {'dtype': 'dtype', 'tz': 'dtype.tz'}])
-    def test_construction_with_alt(self, kwargs):
-        i = pd.date_range('20130101', periods=5, freq='H', tz='US/Eastern')
+    def test_construction_with_alt(self, kwargs, tz_aware_fixture):
+        tz = tz_aware_fixture
+        i = pd.date_range('20130101', periods=5, freq='H', tz=tz)
         kwargs = {key: attrgetter(val)(i) for key, val in kwargs.items()}
         result = DatetimeIndex(i, **kwargs)
         tm.assert_index_equal(i, result)
-        assert result.tz.zone == 'US/Eastern'
 
     @pytest.mark.parametrize('kwargs', [
         {'tz': 'dtype.tz'},
         {'dtype': 'dtype'},
         {'dtype': 'dtype', 'tz': 'dtype.tz'}])
-    def test_construction_with_alt_tz_localize(self, kwargs):
-        i = pd.date_range('20130101', periods=5, freq='H', tz='US/Eastern')
+    def test_construction_with_alt_tz_localize(self, kwargs, tz_aware_fixture):
+        tz = tz_aware_fixture
+        i = pd.date_range('20130101', periods=5, freq='H', tz=tz)
         kwargs = {key: attrgetter(val)(i) for key, val in kwargs.items()}
         result = DatetimeIndex(i.tz_localize(None).asi8, **kwargs)
-        expected = i - pd.Timedelta(hours=5)
+        expected = i.tz_localize(None).tz_localize('UTC').tz_convert(tz)
         tm.assert_index_equal(result, expected)
-        assert result.tz.zone == 'US/Eastern'
 
         # localize into the provided tz
         i2 = DatetimeIndex(i.tz_localize(None).asi8, tz='UTC')
@@ -474,11 +475,15 @@ def test_constructor_with_non_normalized_pytz(self, tz):
         assert pytz.timezone(tz) is result.tz
 
     @pytest.mark.parametrize('klass', [Index, DatetimeIndex])
-    @pytest.mark.parametrize('box', [np.array, list])
-    def test_constructor_with_int_tz(self, klass, box):
+    @pytest.mark.parametrize('box', [
+        np.array, partial(np.array, dtype=object), list])
+    @pytest.mark.parametrize('tz, dtype', [
+        ['US/Pacific', 'datetime64[ns, US/Pacific]'],
+        [None, 'datetime64[ns]']])
+    def test_constructor_with_int_tz(self, klass, box, tz, dtype):
         # GH 20997, 20964
-        ts = Timestamp('2018-01-01', tz='US/Pacific')
-        result = klass(box([ts.value]), dtype='datetime64[ns, US/Pacific]')
+        ts = Timestamp('2018-01-01', tz=tz)
+        result = klass(box([ts.value]), dtype=dtype)
         expected = klass([ts])
         tm.assert_index_equal(result, expected)
 

From dc7e5c03d9abba90e3e9b4d3bc3f6f7f77a1aaa4 Mon Sep 17 00:00:00 2001
From: Matt Roeschke <emailformattr@gmail.com>
Date: Wed, 13 Jun 2018 23:34:00 -0700
Subject: [PATCH 11/11] add assertion back after merge conflict

---
 pandas/tests/indexes/datetimes/test_construction.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pandas/tests/indexes/datetimes/test_construction.py b/pandas/tests/indexes/datetimes/test_construction.py
index 318a3234024a6..f7682a965c038 100644
--- a/pandas/tests/indexes/datetimes/test_construction.py
+++ b/pandas/tests/indexes/datetimes/test_construction.py
@@ -494,6 +494,7 @@ def test_constructor_with_int_tz(self, klass, box, tz, dtype):
         ts = Timestamp('2018-01-01', tz=tz)
         result = klass(box([ts.value]), dtype=dtype)
         expected = klass([ts])
+        assert result == expected
 
 
 class TestTimeSeries(object):