Today is February 29th, a leap year. My son mentioned a classmate of his told him he had a leap year birthday. Poor kid, in actual Feb. 29th birthdays, today is this young man's 5th birthday. It could have been worse though. Had he been born a century earlier, he would have had only 4 actual Feb. 29th birthdays. How would that be possible for a 20 year old? Ask Pope Gregory.
Back in Julius Caesars day--45 BC--the concept of adding a day to the 365 day calendar every 4 years was introduced. It was known that an actual year was almost 1/4 day longer than 365 day year. So to compensate, Caesar added the leap year day to his Julian Calendar. This worked for a while.
Pope Gregory, in the 16th century, recognized that Julius' correction was not enough. "Eventually Easter would fall on Christmas Day unless the system was refined. The 'Gregorian Calendar,' still in use today, fine-tunes the leap year calculation by stipulating that century years (e.g. years ending in "00"), which would normally qualify as leap years, are an exception to the general rule and will have only 365 days."* But this still needed a little more adjusting.
If a century year is evenly divisible by 400, then it will have the extra
leap year day. It is an exception to the exception and that is why the
classmate is "5" today instead of "4"!
The amount of error in our Gregorian calendar is about 27 seconds (1 day every 3,236 years). I think we are safe for a while!
* I found this info in a clipping I saved from a pre Y2K Readers Digest(?).
Links: Betterbrookfield, Vicki Mckenna
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