code: public void addTimezonedDate(String tzid, ICalProperty property, ICalDate date) {
  		timezonedDates.put(tzid, new TimezonedDate(date, property));
  	}
docs: Keeps track of a date-time property value that uses a timezone so it can
  be parsed later. Timezones cannot be handled until the entire iCalendar
  object has been parsed.
  @param tzid the timezone ID (TZID parameter)
  @param property the property
  @param date the date object that was assigned to the property object