The Citizen GPS F990 is an amazing watch, and because it knows what time it is anywhere in the world, it is also technically a perpetual calendar. See how it handles the leap year change-over in this video below:
This video was shot by a Citizen fan who owns the watch, who like other watch nerds with perpetual calendars, waited till midnight to see this rare event happen and record it for posterity. Very cool.
Ok, so its not a mechanical perpetual calendar, but it is a very attractive and technologically advanced watch.