code: def _parse_time(time_str, property_name):
          
          if not time_str:
              return
  
          parsed = parse_date(time_str)
          if not parsed:
              raise UserException("Unable to parse the time provided by '{}'".format(property_name))
  
          return to_utc(parsed)
docs: Parse the time from the given string, convert to UTC, and return the datetime object
  
          Parameters
          ----------
          time_str : str
              The time to parse
  
          property_name : str
              Name of the property where this time came from. Used in the exception raised if time is not parseable
  
          Returns
          -------
          datetime.datetime
              Parsed datetime object
  
          Raises
          ------
          samcli.commands.exceptions.UserException
              If the string cannot be parsed as a timestamp