BUG: bug in Series construction from UTC

Author: jreback

doc/source/whatsnew/v0.20.0.txt

@@ -253,7 +253,7 @@ Bug Fixes
 
 
 
-
+- Bug in ``Series`` construction with a datetimetz (:issue:`14928`)
 
 
 

pandas/core/ops.py

@@ -545,9 +545,9 @@ def _offset(lvalues, rvalues):
 
                 # with tz, convert to UTC
                 if self.is_datetime64tz_lhs:
-                    lvalues = lvalues.tz_localize(None)
+                    lvalues = lvalues.tz_convert('UTC').tz_localize(None)
                 if self.is_datetime64tz_rhs:
-                    rvalues = rvalues.tz_localize(None)
+                    rvalues = rvalues.tz_convert('UTC').tz_localize(None)
 
                 lvalues = lvalues.view(np.int64)
                 rvalues = rvalues.view(np.int64)

pandas/tests/series/test_constructors.py

@@ -529,6 +529,21 @@ def test_constructor_with_datetime_tz(self):
         expected = Series(pd.DatetimeIndex(['NaT', 'NaT'], tz='US/Eastern'))
         assert_series_equal(s, expected)
 
+    def test_construction_consistency(self):
+
+        # make sure that we are not re-localizing upon construction
+        # GH 14928
+        s = Series(pd.date_range('20130101', periods=3, tz='US/Eastern'))
+
+        result = Series(s, dtype=s.dtype)
+        tm.assert_series_equal(result, s)
+
+        result = Series(s.dt.tz_convert('UTC'), dtype=s.dtype)
+        tm.assert_series_equal(result, s)
+
+        result = Series(s.values, dtype=s.dtype)
+        tm.assert_series_equal(result, s)
+
     def test_constructor_periodindex(self):
         # GH7932
         # converting a PeriodIndex when put in a Series

pandas/types/cast.py

@@ -823,9 +823,10 @@ def _possibly_cast_to_datetime(value, dtype, errors='raise'):
                         elif is_datetime64tz:
                             # input has to be UTC at this point, so just
                             # localize
-                            value = to_datetime(
-                                value,
-                                errors=errors).tz_localize(dtype.tz)
+                            value = (to_datetime(value, errors=errors)
+                                     .tz_localize('UTC')
+                                     .tz_convert(dtype.tz)
+                                     )
                         elif is_timedelta64:
                             value = to_timedelta(value, errors=errors)._values
                     except (AttributeError, ValueError, TypeError):