BUG: fix align in case of different tz but aligning values

Author: jorisvandenbossche

pandas/core/generic.py

@@ -20,6 +20,7 @@
                                  is_numeric_dtype,
                                  is_datetime64_dtype,
                                  is_timedelta64_dtype,
+                                 is_datetime64tz_dtype,
                                  is_list_like,
                                  is_dict_like,
                                  is_re_compilable)
@@ -4438,13 +4439,23 @@ def _align_frame(self, other, join='outer', axis=None, level=None,
             left = left.fillna(axis=fill_axis, method=method, limit=limit)
             right = right.fillna(axis=fill_axis, method=method, limit=limit)
 
+        # if DatetimeIndex have different tz, convert to UTC
+        if is_datetime64tz_dtype(left.index):
+            if left.index.tz != right.index.tz:
+                if join_index is not None:
+                    left.index = join_index
+                    right.index = join_index
+
         return left.__finalize__(self), right.__finalize__(other)
 
     def _align_series(self, other, join='outer', axis=None, level=None,
                       copy=True, fill_value=None, method=None, limit=None,
                       fill_axis=0):
+
+        is_series = isinstance(self, ABCSeries)
+
         # series/series compat, other must always be a Series
-        if isinstance(self, ABCSeries):
+        if is_series:
             if axis:
                 raise ValueError('cannot align series to a series other than '
                                  'axis 0')
@@ -4503,6 +4514,15 @@ def _align_series(self, other, join='outer', axis=None, level=None,
             left = left.fillna(fill_value, method=method, limit=limit,
                                axis=fill_axis)
             right = right.fillna(fill_value, method=method, limit=limit)
+
+        # if DatetimeIndex have different tz, convert to UTC
+        if is_series or (not is_series and axis == 0):
+            if is_datetime64tz_dtype(left.index):
+                if left.index.tz != right.index.tz:
+                    if join_index is not None:
+                        left.index = join_index
+                        right.index = join_index
+
         return left.__finalize__(self), right.__finalize__(other)
 
     def _where(self, cond, other=np.nan, inplace=False, axis=None, level=None,

pandas/core/ops.py

@@ -622,15 +622,6 @@ def _align_method_SERIES(left, right, align_asobject=False):
 
             left, right = left.align(right, copy=False)
 
-            if is_datetime64tz_dtype(left.index):
-                if left.index.tz != right.index.tz:
-                    # if DatetimeIndex have different tz, convert to UTC
-                    index, lidx, ridx = left.index.join(
-                        right.index, how='outer', return_indexers=True)
-
-                    left.index = index
-                    right.index = index
-
     return left, right
 
 

pandas/tseries/tests/test_timezones.py

@@ -1290,6 +1290,28 @@ def test_align_aware(self):
         self.assertEqual(df1.index.tz, new1.index.tz)
         self.assertEqual(df2.index.tz, new2.index.tz)
 
+        # # different timezones convert to UTC
+
+        # frame
+        df1_central = df1.tz_convert('US/Central')
+        new1, new2 = df1.align(df1_central)
+        self.assertEqual(new1.index.tz, pytz.UTC)
+        self.assertEqual(new2.index.tz, pytz.UTC)
+
+        # series
+        new1, new2 = df1[0].align(df1_central[0])
+        self.assertEqual(new1.index.tz, pytz.UTC)
+        self.assertEqual(new2.index.tz, pytz.UTC)
+
+        # combination
+        new1, new2 = df1.align(df1_central[0], axis=0)
+        self.assertEqual(new1.index.tz, pytz.UTC)
+        self.assertEqual(new2.index.tz, pytz.UTC)
+
+        df1[0].align(df1_central, axis=0)
+        self.assertEqual(new1.index.tz, pytz.UTC)
+        self.assertEqual(new2.index.tz, pytz.UTC)
+
     def test_append_aware(self):
         rng1 = date_range('1/1/2011 01:00', periods=1, freq='H',
                           tz='US/Eastern')