Add docstring for DatetimeIndex.normalize method

Signed-off-by: Tushar Mittal <chiragmittal.mittal@gmail.com>

Author: techytushar

pandas/core/indexes/datetimes.py

@@ -1770,11 +1770,31 @@ def date(self):
 
     def normalize(self):
         """
-        Return DatetimeIndex with times to midnight. Length is unaltered
+        Return DatetimeIndex with times converted to midnight.
+
+        When using DatetimeIndex, the time can be converted to midnight i.e.
+        00:00:00. This is useful in cases, when the time does not matter in
+        DataFrame. Length is unaltered.
 
         Returns
         -------
         normalized : DatetimeIndex
+
+        See Also
+        --------
+        DatetimeIndex.floor : Floor the DatetimeIndex to the specified freq.
+        DatetimeIndex.ceil : Ceil the DatetimeIndex to the specified freq.
+        DatetimeIndex.round : Round the DatetimeIndex to the specified freq.
+
+        Examples
+        --------
+        >>> df = pd.DataFrame({'date':['2015-05-01 18:47:05.060000',
+        ...                            '2014-05-01 18:47:05.110000']})
+        >>> df.date = pd.to_datetime(df.date)
+        >>> df.date[1]
+        Timestamp('2014-05-01 18:47:05.110000')
+        >>> df.date[1].normalize()
+        Timestamp('2014-05-01 00:00:00')
         """
         new_values = conversion.date_normalize(self.asi8, self.tz)
         return DatetimeIndex(new_values, freq='infer', name=self.name,