Why do we have leap years?

By Blake Mathews, Weather producer, meteorologist, bmathews@wjxt.com
Published On: Feb 28 2012 12:19:33 PM EST
Updated On: Feb 28 2012 12:21:18 PM EST

iStock / kutaytanir

JACKSONVILLE, Fla. -

Can you believe it? Today is the last day of February already! Oh wait a minute; it's a leap year.

As if moving our clocks around twice a year isn't bad enough, we also have to add a day to our calendar every four years and for what? Total nonsense? Or is it?

The Earth, the planet in which most of us live on, rotates around the sun. It makes one complete revolution around the sun every 365 days and change.

What ''change'' am I referring to? Well, it actually takes the Earth 365 days, five hours, 48 minutes and 46 seconds to make one complete orbit. Since the Gregorian calendar (the calendar we use) is based on 365 days, that means we must make up for the extra time somewhere. If we didn't, we'd lose six hours every single year.

Over the course of 100 years, our calendar would be off by as much as 24 days. To make up the time difference, we add one day in February every four years.

According to National Geographic and NewsObserver.com, the leap year was invented by the Romans in 46 B.C., credited officially to Julius Caesar, but actually derived by the astronomer Sosigenes at the request of Caesar. By 46 B.C., the date of the spring equinox had slowly shifted about 81 days out of place in the Roman calendar, so Caesar added 81 days to reset the year to the correct date and introduced the leap year to help it stay in the right place.

The Roman leap year was every four years without exception. This version, called the Julian calendar in honor of Julius Caesar, has the average year as 365.2500 days.

Here's a fun thought: According to NewsObserver, if Caesar had never reset the calendar and instituted the leap year, the accumulated error today would be about 580 days. In other words, we would have lost one entire year and an additional 214 days, and today mid-winter would actually be in June. January would be the height of summer vacation season.

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