TORONTO -- Ever wondered why we have leap year? Or exactly what it means for people born on that day? Here are five fun, if complicated, facts to bring you up to speed on the most unusual day of the year:

Why does leap year exist?

Leap year is the reason that seasons occur at the same time each year. According to the Honor Society of Leap Year Day Babies, the Earth takes 365.24 days to make a complete cycle around the sun. Every four years, therefore, the world would be a full day out of synch with the calendar. The society says a person who lived to be 90 would see their birthday drift by three weeks over the course of their lifetime. One extra day added to the end of February every four years prevents this from happening.

How does it work?

According to Irv Bromberg at the University of Toronto, "the Gregorian calendar has a 400-year repeat cycle, in which every year number divisible by four (2016, for example) has a leap day appended to February, except if the year number is divisible by 100, in which case it is a leap year only if the year number is also divisible by 400." For instance, the year 2000 was a leap year, while 1900 was not. Got that?

Are there any drawbacks of being born on leap day?

The estimated five million people with Feb. 29 birthdays, also known as leapers, once had to face a number of day-to-day administrative hassles, according to the society. Insurance companies, banks and other major organizations often didn't recognize leap day as a valid date, forcing people to choose either Feb. 28 or March 1 as their birthday. Evolving technology has made this less of an issue, but some websites still won't accept Feb. 29. Some leapers also complain that companies offering birthday promotions don't wind up delivering for those born on the extra day.

Have any cultural traditions evolved around leap year?

While the origin of the tradition is unknown, leap day became the day on which women of several different cultures were allowed to propose to men rather than waiting to be asked. Some folklore has it that a man was supposed to compensate a woman if he turned down her offer of marriage. Compensation could include everything from silks to kisses. The society insists, though, that this shouldn't be confused with the similarly themed Sadie Hawkins Day, which takes place on Nov. 15.

Are there any celebrity leapers?

According to the society, there have been a handful of famous leapers, some of whom have strong Canadian ties. These include General Louis-Joseph de Montcalm, whose defeat during the Battle of the Plains of Abraham looms large in Canadian history. Others include actress Dinah Shore, film director William Wellman -- whose movie "Wings" became the first ever best picture Oscar winner -- and rapper Ja Rule. Several Canadian hockey players also celebrated Feb. 29 birthdays, including Henri Richard (brother of legendary star Maurice (Rocket) Richard), Cam Ward and Simon Gagne.