code: def value_from_message(self, message):
          
          message = super(DateTimeField, self).value_from_message(message)
          if message.time_zone_offset is None:
              return datetime.datetime.utcfromtimestamp(
                  message.milliseconds / 1000.0)
  
          # Need to subtract the time zone offset, because when we call
          # datetime.fromtimestamp, it will add the time zone offset to the
          # value we pass.
          milliseconds = (message.milliseconds -
                          60000 * message.time_zone_offset)
  
          timezone = util.TimeZoneOffset(message.time_zone_offset)
          return datetime.datetime.fromtimestamp(milliseconds / 1000.0,
                                                 tz=timezone)
docs: Convert DateTimeMessage to a datetime.
  
          Args:
            A DateTimeMessage instance.
  
          Returns:
            A datetime instance.