/**
  * add given recurrence to given set and to nessesary adoptions
  * 
  * @param Calendar_Model_Event      $_recurrence
  * @param Tinebase_Record_RecordSet $_eventSet
  */
 protected static function addRecurrence($_recurrence, $_eventSet)
 {
     $_recurrence->setId('fakeid' . $_recurrence->uid . $_recurrence->dtstart->getTimeStamp());
     // adjust alarms
     if ($_recurrence->alarms instanceof Tinebase_Record_RecordSet) {
         foreach ($_recurrence->alarms as $alarm) {
             $alarm->alarm_time = clone $_recurrence->dtstart;
             $alarm->alarm_time->subMinute($alarm->getOption('minutes_before'));
         }
     }
     $_eventSet->addRecord($_recurrence);
 }