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Today Is Leap Day

By Cherri Gregg

PHILADELPHIA (CBS) - Today is Leap Day, just an ordinary day for most folks -- some people didn't even know about it.

February 29th only comes once every four years, which is often enough to remember, yet rare enough to forget.

But what is leap day exactly?

Temple University math professor Yury Grabovsky has given lectures on the topic and says Leap Day exists because it actually takes about 365 and a quarter days for the earth to revolve around the sun.

"After four years, you get a day error, after 40 years, you get 10 days error. So as you can see, the error adds up over time."

He says adding an extra day in most years divisible by four helps to correct the error and ensures that the seasons start when expected.

"The system is very simple and very precise."

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