Leap Year: Who Invented It and How It Works

Today is Leap Day -- an extra day added every four years to make up for the fact that our year is actually 365.242374 days and not, as Kindergardeners are commonly taught, 365 days.

Every year divisible by four (such as 2012) the year then becomes one day longer.

Of course, it's not really that simple.

Because the year is actually 365.242374 days and not 365.25 days, every 400 years we have to give back a few days. Therefore, century years are only leap years if they're divisble by four. 2000 was a leap year, but if you make it to 2100 you won't get that extra day.

This system was first developed by Julius Caesar, who developed much of our current calendar. In 1582 it was formalized by Pope Gregory XIII, who developed the current model.

Because Feb. 29 is relatively rare it has become imbued with superstititions and traditions -- viewed as an "extra" day.

As that 2010 terrible movie of the same name explained, Leap Day in Irish and Scottish traditions was a day for women to propose to men instead of the other way around. Crazy.

Leap Day babies were also traditionally considered unlucky (probably because they'd get fewer birthday parties), but I'd like to think those birthdays that come around every four years are extra-special.

More recently, Leap Day has been growing in pop culture popularity thanks to shows like 30 Rock, which celebrated the fictional holiday of Leap Day with the mythical Leap Day William, who legend has it emerges from the Mariana Trench to give kids candy and encourage adults to take advantage of the magic of Leap Day. 'Real life is for March 1.'

What will you do for Leap Day?