Got this from WIRED Magazine issue 16.023 Smart Things About Leap Years
1) A leap year is any year evenly divisible by four-except for century years, which have to be divisible by 400.It's Not a perfect system: The Gregorian year is 27 seconds longer that the astronomical year. By 12008 [if earth is around that long lol], we'll be three days off.
2) October 5-14 1582, never happened in Catholic land. Brits (and their American subjects) born September 3 to 13 had no birthday in 1752. Those days were dropped when the western world switched fromfrom the Julian to the Gregorian calendar.
3) International Atomic Time -Kept by ultra precise clocks is gradually out pacing astronomical time, which is determined by our planet'srotation. (Earth's Spin is slowing - what a drag.) So in 1972 the International Earth Rotationand Reference Systems Service begin adding occasional leap seconds. They've done it 23 times most recently adding an extra "One-Mississippi" on December 31, 2005.
