BUG: DatetimeIndex localizes twice if input is localized DatetimeIndex #1838

Author: Chang She

pandas/tseries/index.py

@@ -242,10 +242,13 @@ def __new__(cls, data=None,
         else:
             if tz is not None:
                 tz = tools._maybe_get_tz(tz)
-                # Convert local to UTC
-                ints = subarr.view('i8')
 
-                subarr = lib.tz_localize_to_utc(ints, tz)
+                if (not isinstance(data, DatetimeIndex) or
+                    getattr(data, 'tz', None) is None):
+                    # Convert tz-naive to UTC
+                    ints = subarr.view('i8')
+                    subarr = lib.tz_localize_to_utc(ints, tz)
+
                 subarr = subarr.view(_NS_DTYPE)
 
         subarr = subarr.view(cls)

pandas/tseries/tests/test_timezones.py

@@ -656,6 +656,12 @@ def test_timestamp_equality_different_timezones(self):
         self.assert_((utc_range == berlin_range).all())
         self.assert_((berlin_range == eastern_range).all())
 
+    def test_datetimeindex_tz(self):
+        rng = date_range('03/12/2012 00:00', periods=10, freq='W-FRI',
+                         tz='US/Eastern')
+        rng2 = DatetimeIndex(data=rng, tz='US/Eastern')
+        self.assert_(rng.equals(rng2))
+
 if __name__ == '__main__':
     nose.runmodule(argv=[__file__,'-vvs','-x','--pdb', '--pdb-failure'],
                    exit=False)