Leap Day!

So, this is an excerpt from an email that a friend of mine sent me: "The Julian Calendar, adopted by Julius Caesar...ages ago, was found in about 730AD to be about 11 minutes off, resulting in about 1 missed day in 128. Well, as most bureaucracies go, this tidbit was ignored till 1582. By this time they figured that the error was about 10 days. To correct this Pope Gregory XIII decreed that the following day (Oct 4) would instead be Oct 15. [Wouldn't it be cool to have that power!] "Anyways, our current calendar has the same issues. A year is measured by how long it takes the Earth to revolve around the sun and get back to the exact same spot. As it turns out the "year" dictated by our calendar undershoots this by about a 1/4 day. So every 4 years we throw an extra day in for good measure. Yet this still isn't exact, so to further complicate things we onlyhave leap years on years that end with 00 IF it is divisible by 400. So 1600 and 2000 had leap years, but 1700, 1800 and 1900 didn't." Kinda crazy. If I'm alive in 2100, apparently we don't get an extra day even though it would technically be a leap year.