If your locale is one in which the Gregorian calendar is standardly used, then you'll get a GregorianCalendar object from that. And theoretically if there were other subclasses of Calendar -- such as an Islamic or Ethiopian or Japanese calendar -- then using for example Locale.JAPAN might return a Japanese calendar. But there aren't any other subclasses of Calendar, at least not in
Java 5, so you always get a GregorianCalendar. It's a factory method.
(Later edit
Calendar.getInstance(Locale.US) and Calendar.getInstance(Locale.FRANCE) do work differently -- for example they return different values from getFirstDayOfWeek().
[ June 29, 2006: Message edited by: Paul Clapham ]