code: private void setCalendar(Calendar c, boolean update) {
  		if (c == null) {
  			setDate(null);
  		}
  		Calendar oldCalendar = calendar;
  		calendar = c;
  
  		if (update) {
  			// Thanks to Jeff Ulmer for correcting a bug in the sequence :)
  			yearChooser.setYear(c.get(Calendar.YEAR));
  			monthChooser.setMonth(c.get(Calendar.MONTH));
  			dayChooser.setDay(c.get(Calendar.DATE));
  		}
  
  		firePropertyChange("calendar", oldCalendar, calendar);
  	}
docs: Sets the calendar attribute of the JCalendar object
  
  @param c
  the new calendar value
  @param update
  the new calendar value
  @throws NullPointerException -
  if c is null;