The year 2000 is not supposed to be a Leap Year. Yet it is because of a little known three-step century rule: Any year divisible by 4 is a Leap Year, except years divisible by 100, unless the years are divisible by 400. Therefore, some PCs that squeeked past New Years' Day might stumble on the way to March 1, 2000.
What May Happen
The greatest risk is to custom software because some programmers may not have counted on 2000 as a Leap Year, allowing February 28th to roll into March 1st. Having said that, John Koskinen, the head of the President's Council on Y2K Conversion, does not expect major systems to fail because in the course of rigorous Y2K testing last year, at least 30 potential Y2K problem dates were flagged and checked, among them was February 29, 2000. Nonetheless, the government will be operating its Y2K Task Force from February 28th through March 1st, issuing press conferences each day to report on computer systems worldwide.
What You Can Do
Windows, DOS, Mac and Linux operating systems are not affected by the Leap Day problem. However, some application software may either calculate or report the wrong date. So far only Micosoft has issued a leap day patch for Excel 2000 (note that no other versions of Excel are affected). Users are encouraged to contact the appropriate software vendor should any date-related problems occur.
