Calendar Facts and Trivia
Each century is named for the LAST year in it. We are currently in the
21st Century, which makes 2100 the last year of the century, not the first year of the next.
There was no year 0, and each century lasts one hundred years. The first century was from 1 AD to 100 AD. The second from 101 AD to 200 AD, etc.
The same thing applies to millenniums, only that they last one thousand years. The first was from 1 AD to 1000 AD, and the current one from 1001 AD to 2000 AD.
Every year that is divisible by 4 evenly is a leap year. EXCEPT for those also divisible by 100 evenly. Even this exception has an exception: When the year is the last in a millennium, it becomes a leap year after all.