This option show/hide the extra month days by setting the property CalendarComponent.SHOW_EXTRA_MONTH_DAYS to true/false.
The code below shows how to show/hide the extra month days: 
<CODE>
CalendarComponent calendarComponent = new CalendarComponent();
//    show extra month days
calendarComponent.setCalendarProperty(CalendarComponent.SHOW_EXTRA_MONTH_DAYS, new Boolean(true));
//    hide extra month days
calendarComponent.setCalendarProperty(CalendarComponent.SHOW_EXTRA_MONTH_DAYS, new Boolean(false));
</CODE>