// e.g. "How long is it from 18:30 to 10 pm?"
sS ai_clockTimeBot_howLongBetween(S s) {
  //if (!matchX("...how long...", s)) null;
  L<Int> clocktimes = map clockTimeMinutesFromFields(pAttractor_allMatches3(
    ll(new ClockTimeAttractor_AM_PM, new ClockTimeAttractor_colon),
    javaTok(s)));
  ret n2(second(clocktimes)-first(clocktimes), "minute");
}