// month = 1 to 12
static long timestampFromYMDHM(int y, int m, int d, int h, int minutes) {
  ret new GregorianCalendar(y, m-1, d, h, minutes).getTimeInMillis();
}

static long timestampFromYMDHM(int y, int m, int d, int h, int minutes, TimeZone tz) {
  ret new Calendar.Builder()
    .setTimeZone(tz)
    .setDate(y, m-1, d).setTimeOfDay(h, minutes, 0)
    .build().getTimeInMillis();
}

Began life as a copy of #1011261