Originally Posted by marklondon

Not much calculation needed:

In general, every year divisible by 4 is a leap year.

Exceptions:
If the year is divisible by 100 then it's NOT a leap year.

Exception to the Exceptions:
If the year is divisible by 400, then it IS a leap year.

So 1980 is a leap year (divisible by 4).
2000 is a leap year (divisible by 400).
1900, 1800, 1700 are not leap years (divisible by 100, but not 400).

Thus endeth the lesson.