ENH: intersection on DatetimeIndex with empty fails for monotonic with anchored offset

Author: changhiskhan

pandas/tseries/index.py

@@ -964,6 +964,10 @@ def intersection(self, other):
                     result.offset = to_offset(result.inferred_freq)
             return result
 
+        if len(self) == 0:
+            return self
+        if len(other) == 0:
+            return other
         # to make our life easier, "sort" the two ranges
         if self[0] <= other[0]:
             left, right = self, other

pandas/tseries/tests/test_timeseries.py

@@ -2155,6 +2155,14 @@ def test_intersection(self):
         result = rng.intersection(rng2)
         self.assert_(result.equals(rng))
 
+        #empty same freq GH2129
+        rng = date_range('6/1/2000', '6/15/2000', freq='T')
+        result = rng[0:0].intersection(rng)
+        self.assert_(len(result) == 0)
+
+        result = rng.intersection(rng[0:0])
+        self.assert_(len(result) == 0)
+
     def test_date_range_bms_bug(self):
         # #1645
         rng = date_range('1/1/2000', periods=10, freq='BMS')