1990 wasn't a leap year. the leap years are "....84', 88', 92', 96', 00', 04', 08', etc...." EDIT: I know, I read the question wrong

1900 was not a leap year because 1900 is not divisible by 400. Read ahead for some good information about which years are leap years: In the Gregorian calendar, a normal year consists of 365 days. Because the actual length of a sidereal year (the time required for the Earth to revolve once about the Sun) is actually 365.2422 days, a "leap year" of 366 days is used once every four years to eliminate the error caused by three normal (but short) years. This would make any year that is evenly divisible by 4 a leap year: for example, 1988, 1992, and 1996 are leap years. However, there is still a small error that must be accounted for (because the extra amount of days in the sidereal year are not quite a quarter day... .2422 is less than .25). To eliminate this error, the Gregorian calendar stipulates that a year that is evenly divisible by 100 (for example, 1900) is a leap year only if it is also evenly divisible by 400. For this reason, the following years ARE NOT leap years 1700, 1800, 1900, 2100, 2200, 2300, 2500, 2600 because they are evenly divisible by 100 but NOT by 400. The following years ARE leap years 1600, 2000, 2400 because they are evenly divisible by both 100 and 400. ------------------------------- The above information was taken from http://support.microsoft.com/?kbid=214019 ... EXCEPT, as Bob pointed out... their 365.25etc number for how many days are in a year appears to be incorrect. I changed that one item in the answer above to reflect the number of days the website below uses for its calculation, which seems to be more correct. Bob's comments make sense. http://www.timeanddate.com/date/leapyear.html

---i guess they just leaped over it---