> However, there is still a small error that must be accounted for. 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:
"We establish that a bissextile [366th day] shall be inserted every four years (as with the present custom), except in centennial years. So the years 1700, 1800, and 1900 will not be leap years. Assuredly, the year 2000 will have an extra day in it." -- Greg XIII, 1582
Edit: no it's not, it's absolutely correct, leap years just aren't as simple as I thought!