code: def _parse_interval(value):
      
      try:
          return sorted(aniso8601.parse_interval(value))
      except ValueError:
          try:
              return aniso8601.parse_datetime(value), None
          except ValueError:
              return aniso8601.parse_date(value), None
docs: Do some nasty try/except voodoo to get some sort of datetime
      object(s) out of the string.