Leap Years are years divisible by four, with two exceptions.
1. "Century" year numbers (divisible evenly by 100) are not leap
years.
2. Years divisible evenly by 400 ARE leap years.
So years like 1992 and 1996 were leap years. Century years like
1900 or 2100 are NOT leap years. But 2000 was a leap year, and 2400
will be.