Trouble is, JavaScript will *NOT* display Feb 29, 1900 or Feb 29, 2100.
If you do
Code:
var theDate = new Date( 1900, 1, 29 ); // 1 is February in JS code
document.write( theDate );
JavaScript *will* display "March 1, 1900" back at you.
So in order to display "Feb 29, 1900" you will have to not use JavaScript's Date() object *AT ALL* and essentially re-create the entire calendar system.
Of course it can be done. It's just a real pain in the patootie and you are asking a lot to have somebody write that all for you.