function getScheduleTotalTime($start, $end, $schedule_policy_id)
 {
     $sf = new ScheduleFactory();
     $sf->setStartTime(TTDate::parseDateTime($start));
     $sf->setEndTime(TTDate::parseDateTime($end));
     $sf->setSchedulePolicyId($schedule_policy_id);
     $sf->preSave();
     return TTDate::getTimeUnit($sf->getTotalTime());
 }