code: Rule Time_HH_MM_SS() {
          return Sequence(
                  OneOrTwoDigits(), ':',
                  TwoDigits(),
                  FirstOf(Sequence(':', TwoDigits()), push(0)),
                  EOI,
                  swap3() && push(convertToTime(popAsInt(), popAsInt(), popAsInt()))
          );
      }
docs: h(h)?:mm(:ss)?