Remove from start/end dates if tz is not None (#7901, #7835)

doc/source/timeseries.rst

@@ -1364,6 +1364,12 @@ tz-aware data to another time zone:
        is localized using one version and operated on with a different version.  
        See :ref:`here<io.hdf5-notes>` for how to handle such a situation.
 
+.. warning::
+
+       It is incorrect to pass a timezone directly into the ``datetime.datetime`` constructor (e.g.,
+       ``datetime.datetime(2011, 1, 1, tz=timezone('US/Eastern'))``.  Instead, the datetime
+       needs to be localized using the the localize method on the timezone.
+
 Under the hood, all timestamps are stored in UTC. Scalar values from a
 ``DatetimeIndex`` with a time zone will have their fields (day, hour, minute)
 localized to the time zone. However, timestamps with the same UTC value are

doc/source/v0.15.0.txt

@@ -358,7 +358,9 @@ Bug Fixes
 
 
 - Bug in ``GroupBy.filter()`` where fast path vs. slow path made the filter
-  return a non scalar value that appeared valid but wasnt' (:issue:`7870`).
+  return a non scalar value that appeared valid but wasn't (:issue:`7870`).
+- Bug in ``date_range()``/``DatetimeIndex()`` when the timezone was inferred from input dates yet incorrect
+  times were returned when crossing DST boundaries (:issue:`7835`, :issue:`7901`).  
 
 
 

pandas/tseries/index.py

@@ -416,7 +416,7 @@ def _generate(cls, start, end, periods, name, offset,
 
         else:
 
-            if inferred_tz is None and tz is not None:
+            if tz is not None:
                 # naive dates
                 if start is not None and start.tz is not None:
                     start = start.replace(tzinfo=None)

pandas/tseries/tests/test_daterange.py

@@ -354,25 +354,51 @@ def test_range_bug(self):
     def test_range_tz_pytz(self):
         # GH 2906
         tm._skip_if_no_pytz()
-        from pytz import timezone as tz
+        from pytz import timezone
 
-        start = datetime(2011, 1, 1, tzinfo=tz('US/Eastern'))
-        end = datetime(2011, 1, 3, tzinfo=tz('US/Eastern'))
+        tz = timezone('US/Eastern')
+        start = tz.localize(datetime(2011, 1, 1))
+        end = tz.localize(datetime(2011, 1, 3))
 
         dr = date_range(start=start, periods=3)
-        self.assertEqual(dr.tz, tz('US/Eastern'))
+        self.assertEqual(dr.tz.zone, tz.zone)
         self.assertEqual(dr[0], start)
         self.assertEqual(dr[2], end)
 
         dr = date_range(end=end, periods=3)
-        self.assertEqual(dr.tz, tz('US/Eastern'))
+        self.assertEqual(dr.tz.zone, tz.zone)
         self.assertEqual(dr[0], start)
         self.assertEqual(dr[2], end)
 
         dr = date_range(start=start, end=end)
-        self.assertEqual(dr.tz, tz('US/Eastern'))
+        self.assertEqual(dr.tz.zone, tz.zone)
         self.assertEqual(dr[0], start)
         self.assertEqual(dr[2], end)
+
+    def test_range_tz_dst_straddle_pytz(self):
+
+        tm._skip_if_no_pytz()
+        from pytz import timezone
+        tz = timezone('US/Eastern')
+        dates = [(tz.localize(datetime(2014, 3, 6)), 
+                  tz.localize(datetime(2014, 3, 12))),
+                 (tz.localize(datetime(2013, 11, 1)), 
+                  tz.localize(datetime(2013, 11, 6)))]
+        for (start, end) in dates:
+            dr = date_range(start, end, freq='D')
+            self.assertEqual(dr[0], start)
+            self.assertEqual(dr[-1], end)
+            self.assertEqual(np.all(dr.hour==0), True)
+
+            dr = date_range(start, end, freq='D', tz='US/Eastern')
+            self.assertEqual(dr[0], start)
+            self.assertEqual(dr[-1], end)
+            self.assertEqual(np.all(dr.hour==0), True)        
+
+            dr = date_range(start.replace(tzinfo=None), end.replace(tzinfo=None), freq='D', tz='US/Eastern')
+            self.assertEqual(dr[0], start)
+            self.assertEqual(dr[-1], end)
+            self.assertEqual(np.all(dr.hour==0), True)        
 
     def test_range_tz_dateutil(self):
         # GH 2906