The
divisible by
2000 and divisible by
5000 have never been adopted by any
country, anywhere. It all relates back to the
Gregorian Calendar. So 2000, is a leap year. It looks like
Microsoft got this one right. "The 2000 not a leap year," though thoroughly debunked is another of those
urban legends to pass around the net for many years.
One should note that a year is a leap year if it is divisible by 4. Unless it is divisible by 100; however, if it is divisible by 400 it is a leap year. There are no further rules.
For more information: <http://aa.usno.navy.mil/AA/faq/docs/leap_years.html>
also http://www.merlyn.demon.co.uk/leapyear.htm