protected String getRecurrence(TZSRecurrence tzsRecurrence) {
    if (tzsRecurrence == null) {
      return null;
    }

    Recurrence recurrence = new Recurrence();

    Frequency frequency = _frequencyMap.get(tzsRecurrence.getFrequency());

    int interval = tzsRecurrence.getInterval();

    List<Weekday> weekdays = new ArrayList<Weekday>();

    if ((frequency == Frequency.DAILY) && (interval == 0)) {
      frequency = Frequency.WEEKLY;

      interval = 1;

      weekdays.add(Weekday.MONDAY);
      weekdays.add(Weekday.TUESDAY);
      weekdays.add(Weekday.WEDNESDAY);
      weekdays.add(Weekday.THURSDAY);
      weekdays.add(Weekday.FRIDAY);
    } else if (frequency == Frequency.WEEKLY) {
      DayAndPosition[] dayAndPositions = tzsRecurrence.getByDay();

      for (DayAndPosition dayAndPosition : dayAndPositions) {
        Weekday weekday = _weekdayMap.get(dayAndPosition.getDayOfWeek());

        weekdays.add(weekday);
      }
    }

    recurrence.setInterval(interval);
    recurrence.setFrequency(frequency);
    recurrence.setWeekdays(weekdays);

    Calendar untilJCalendar = tzsRecurrence.getUntil();

    int ocurrence = tzsRecurrence.getOccurrence();

    if (untilJCalendar != null) {
      recurrence.setUntilJCalendar(untilJCalendar);
    } else if (ocurrence > 0) {
      recurrence.setCount(ocurrence);
    }

    return RecurrenceSerializer.serialize(recurrence);
  }
  public void deleteCalendarBookingInstance(
      long calendarBookingId, long startDate, boolean allFollowing)
      throws PortalException, SystemException {

    CalendarBooking calendarBooking =
        calendarBookingPersistence.findByPrimaryKey(calendarBookingId);

    java.util.Calendar jCalendar = JCalendarUtil.getJCalendar(startDate);

    Recurrence recurrenceObj = calendarBooking.getRecurrenceObj();

    if (allFollowing) {
      jCalendar.add(java.util.Calendar.DATE, -1);

      recurrenceObj.setUntilJCalendar(jCalendar);
    } else {
      recurrenceObj.addExceptionDate(jCalendar);
    }

    calendarBooking.setRecurrence(RecurrenceSerializer.serialize(recurrenceObj));

    calendarBookingPersistence.update(calendarBooking, false);
  }