Happy Leap Day!

Yes, every four years we add a day in February to compensate for the fact that it takes the Earth slightly longer than 365 days to orbit the Sun once (about 5 hours and 49 minutes longer). But did you know that every 100 years we don’t have a leap year because by adding the extra day every four years we end up adding too much? There’s one other exception to the rule. Every 400 years we do have a leap year.

Here’s the rule of thumb: If the year is divisible by 4, then it’s a leap year. If the year is divisible by 100, then it’s not a leap year. But, if the year is divisible by 400 then it is a leap year.

Have I totally confused you? If you’re really interested in finding out why you can follow the math at Bad Astronomy or the history in this op-ed.

2 Responses to Happy Leap Day!

  1. Don Singleton February 29, 2008 at 6:48 am #

    It may be a leap day, but this leap year will not have any leap seconds

  2. Silke February 29, 2008 at 9:57 am #

    Wow, I didn’t know that. Thanks, Don.

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