PR for Pandas issue #14872 / fillna() TZ datetime64 rounded

doc/source/whatsnew/v0.19.2.txt

@@ -38,6 +38,7 @@ Other Enhancements
 Bug Fixes
 ~~~~~~~~~
 
+- Bug in fillna() in which timezone aware datetime64 values were incorrectly rounded (:issue:'14872')
 - Compat with ``dateutil==2.6.0``; segfault reported in the testing suite (:issue:`14621`)
 - Allow ``nanoseconds`` in ``Timestamp.replace`` as a kwarg (:issue:`14621`)
 - Bug in ``pd.read_csv`` in which aliasing was being done for ``na_values`` when passed in as a dictionary (:issue:`14203`)

pandas/tests/series/test_missing.py

@@ -17,6 +17,9 @@
 
 from .common import TestData
 
+import datetime
+import pytz
+
 
 def _skip_if_no_pchip():
     try:
@@ -908,6 +911,24 @@ def test_interp_timedelta64(self):
                           index=pd.to_timedelta([1, 2, 4]))
         assert_series_equal(result, expected)
 
+    # GH 14872
+    def test_dtype_utc():
+
+        data = pd.Series([pd.NaT, pd.NaT,
+                          datetime.datetime(2016, 12, 12, 22, 24, 6, 100001,
+                                            tzinfo=pytz.utc)])
+
+        filled = data.fillna(method='bfill')
+
+        expected = pd.Series([
+                             datetime.datetime(2016, 12, 12, 22, 24, 6,
+                                               100001, tzinfo=pytz.utc),
+                             datetime.datetime(2016, 12, 12, 22, 24, 6,
+                                               100001, tzinfo=pytz.utc),
+                             datetime.datetime(2016, 12, 12, 22, 24, 6,
+                                               100001, tzinfo=pytz.utc)])
+
+        assert_series_equal(filled, expected)
 
 if __name__ == '__main__':
     import nose