This is fascinating and complicated stuff. I've just checked with my Windows95 calendar and it reports that February in the year 2000 has 29 days, so it's final. Year 2000 is a leap year ;)))) Now I'm no mathematician but I can't think of a year (at least in the future) that's divisible by 400 and not divisible by 4, so can we do away with the first rule ("divisible by 400")? That would leave "evenly divisible by 4 AND not evenly divisible by 100". The next such year is 2100 (according to my truly poor math skills), that's 104 years from now. So won't "divisible by four" do for now or is an exact calculation of leap years necessary as we are actually producing systems that have an expected life span of more than 100 years ? or perhaps our software calculations take into account the next two centuries ? or perhaps this list only needs a spark.....:) Costas