About every four years, February gets an extra day. We have a leap year so our calendars don't get out of whack, but Feb. 29 has also spurred some interesting traditions. Here are some things you might not know about that this underappreciated winter holiday.

Why we have a leap day

It takes the Earth about 365.242189 days — or 365 days, 5 hours, 48 minutes and 45 seconds — to circle once around the sun, says timeanddate.com. However, the Gregorian calendar we rely on has only 365 days, so if we didn't add an extra day about every four years, we would lose almost six hours every year. After a century, our calendar would be off by about 24 days.

Caesar and the pope

Julius Caesar introduced the first leap year around 46 B.C., but his Julian calendar had only one rule: Any year evenly divisible by four would be a leap year. That created too many leap years, but the math wasn't tweaked until Pope Gregory XIII introduced his Gregorian calendar more than 1,500 years later.

Technically, it's not every four years

Caesar's concept wasn't bad, but his math was a little off: There's a leap year every year that is divisible by four, except for years that are both divisible by 100 and not divisible by 400. The year 2000 was a leap year, but the years 1700, 1800 and 1900 were not. The added rule about centuries (versus just every four years) was an additional fix to make up for the fact that an extra day every four years is too much of a correction, reports ScienceWorld.

Popping the question

woman proposing to manOn leap day, tradition says it's OK for a woman to propose to a man. But who gets the ring? (Photo: Antonio Guillem/Shutterstock)

According to tradition, it's OK for a woman to propose to a man on Feb. 29. The BBC says the custom has been attributed to various historical figures including St. Bridget, who is said to have complained to St. Patrick that women had to wait too long for their suitor to pop the question. The obliging Patrick supposedly gave women one day to propose.

A day that doesn't legally exist

Another tale claims that Queen Margaret of Scotland (who would have been only 5 years old at the time, so take it with a grain of salt) enacted a law setting fines for men who turned down marriage proposals from women during a leap year. It's thought that the basis for the tradition likely goes back to the time when Feb. 29 wasn't recognized by English law; if the day had no legal status, it was OK to break with convention and a woman could propose.

The fine for not accepting

There are other traditions that put a price on saying "no." If a man doesn't accept a leap year proposal, it will cost him. In Denmark, a man refusing a woman’s Feb. 29 proposal must give her a dozen pairs of gloves, according to the Mirror. In Finland, an uninterested gentleman must give his spurned suitor enough fabric to make a skirt.

Bad marriage business

Not surprisingly, leap years can be bad for the nuptial business, too. One in five engaged couples in Greece avoid tying the knot in a leap year, reports the Telegraph. Why? Because they believe it's bad luck.

Leap year capital

The twin cities of Anthony, Texas, and Anthony, New Mexico, are the self-proclaimed Leap Year Capital of the World. They hold a four-day leap year festival each leap year that includes a huge birthday party for all leap year babies. (ID required.)

Leap year babies

four cupcakes with candlesWhen it's not a leap year, leapers have to celebrate on Feb. 28 or March 1. (Photo: Neirfy/Shutterstock)

People born on leap day are often called "leaplings" or "leapers." Most of them don't wait every four years to celebrate their birthdays, but instead blow out the candles on Feb. 28 or March 1. According to History.com, about 4.1 million people around the world have been born on Feb. 29, and the chances of having a leap birthday are one in 1,461.

Record-holding leap year babies

According to Guinness World Records, the only verified example of a family producing three consecutive generations born on Feb. 29 belongs to the Keoghs. Peter Anthony Keogh was born in Ireland in 1940. His son, Peter Eric, was born in the U.K. on leap day in 1964, and his granddaughter Bethany Wealth was born on Feb. 29 in the U.K. in 1996. (We think that's kinda freaky.)

Famous leapers

Famous people born on leap day include composer Gioacchino Rossini, motivational speaker Tony Robbins, jazz musician Jimmy Dorsey, actors Dennis Farina and Antonio Sabato Jr., and rapper/actor Ja Rule.

Leap year proverbs

There are lots of proverbs that revolve around leap year. In Scotland, leap year is thought to be bad for livestock, which is why Scottish say, "Leap year was ne’er a good sheep year." In Italy, where they say "anno bisesto, anno funesto" (which means leap year, doom year), there are warnings against planning special activities such as weddings. The reason? "Anno bisesto tutte le donne senza sesto" which means "In a leap year, women are erratic."

There's even a leap year club

The Honor Society of Leap Year Day Babies is a club for people born on Feb. 29. More than 10,000 people worldwide are members. The goal of the group is to promote leap day awareness and to help leap day babies get in touch.

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.