sS formatHoursMinutesColonSeconds(double seconds) {
  ret formatHoursMinutesColonSeconds(toMS(seconds));
}

sS formatHoursMinutesColonSeconds(long ms) {
  long seconds = iround(toSeconds(ms));
  long hours = seconds/(60*60);
  S s = "";
  if (hours > 0) {
    s = hours + ":";
    seconds -= hours*60*60;
    s += formatInt(seconds/60, 2);
  } else
    s = str(seconds/60);
  ret s + ":" + formatInt(mod(seconds, 60), 2);
}

Began life as a copy of #1020551