Leap Day

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The old calendar rule, "30 days has September...," works just fine for 11 of the 12 months. But that part about February is a little tricky. Not only is February the shortest month of the year, it's the only one that changes. And today is the day that happens -- Leap Day. It keeps the calendar in sync with the true seasons.

The modern calendar actually dates back to ancient Egypt, where the year was divided into 12 months of 30 days each. Five days were added to the end of the year, for a total of 365 days.

Later, the Romans adopted a 12-month calendar, too. But it was a bit of a mess. The months were different lengths, and leap days and months were added pretty much at whim. And even then, it didn't stay aligned with the seasons.

Julius Caesar changed all that in 46 BC, when he ordered an overhaul. The new calendar consisted of today's 12 months, which totaled 365 days. But it takes almost six hours longer than that for Earth to complete one full circle around the Sun, so an extra day was added to every year divisible by four -- years like 2008.

Even that still wasn't quite right, so the calendar began to drift away from the true seasons. So in 1582, Pope Gregory the 13th ordered one more change. He dropped three leap days for every 400 years. The resulting calendar is so accurate that it'll take several thousand years for it to drift even one day away from the true seasons.

Script by Damond Benningfield, Copyright 2007

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