What happens once every four years and can bring anything from unbridled joy to thoughts of inescapable curses?

No, not the World Cup. A leap year, of course, and with it the day of February 29.

Those born on this particular date — some five million people worldwide, known as Leaplings or Leapers — face the dilemma of choosing which day to celebrate their birthday on during non-leap years. But they can also look forward to a special milestone when the date actually appears in the calendar, as is the case in 2024.

In Ireland, February 29 is known as Bachelor's Day, or Lady's Privilege, and has traditionally been viewed as a day when women may propose to men, based on the legend of Saint Bridget and Saint Patrick.

It is said that Saint Bridget, a fifth-century nun, struck a deal with Saint Patrick, the patron saint of Ireland, that allowed women to propose to men on this special day.

Apparently, the tradition was further strengthened by a Scottish law adopted back in 1288, when it was still illegal for women to ask men to marry them; an exception was made that allowed them to do so on a February 29. The law even stated that if a man declined the proposal on this day, he would have to pay a fine.

Other interpretations of the tradition rather base it on a time when English law did not recognize February 29 as a legal day; women were inspired by that bureaucratic loophole to take the lead in getting engaged.

By the 1900s, the tradition of roles-reversed proposals had spread to the United States.

The 2010 movie "Leap Year" was inspired by this tradition. The romantic comedy follows real estate stager Anna, played by Amy Adams, as she travels from Boston to Dublin on the Irish Bachelor's Day to meet her boyfriend, Jeremy (Adam Scott), and ask him to marry her.

The idea of women proposing on the last day of February in a leap year was also taken up in Denmark and Finland.

In Denmark, the custom states that a man who'd rather stay single must give the rejected woman 12 pairs of gloves, which would be enough for her to hide the shame that she has no ring to show off. In Finland, the man must provide the woman with enough fabric to sew a skirt, though the link to the lack of a marriage proposal is less clear.

In some countries, leap years are thought to bring bad luck.

As for Germany, according to an old farmers' proverb, "Schaltjahr gleich Kaltjahr." Simply put: A leap year will be a cold year.

One rather happy German tradition gets a new twist every four years, though not directly on February 29. In non-leap years, on the night before May 1, teenage boys in the Rhine region fell birch trees, decorate them with streamers and affix them to the front of the house of the girl they admire — making a tall and public decoration of love. In leap years, the tradition is reversed and it's the girls' turn to do it.

Globally, the general consensus does point to bad luck, though.

In Taiwan, for example, the year with an extra day is deemed unlucky because many believe that elderly parents are more likely to die every four years. To help promote longevity, married daughters must return home during the leap year with noodles for their parents. The noodle dish is so delicious and healthy that there is a chance it can fight back against the misfortune that the year might bring.

The theme of marriage and bad luck comes together in holy matrimony in Greece, where exchanges of vows on February 29 are to said to be riddled with bad luck; those marriages are destined to end in divorce.

Likewise, if you're misguided enough to get a divorce on a the same date, the Greeks believe you're doomed to never find love again.

If you're in need of a leap year boost, head to Anthony, a town on the Texas-New Mexico border.

It hosts an annual, multi-day leap year festival with origins in the friendship between so-called "29-ers" Mary Ann Brown and Birdie Lewis, who pitched the idea to the town council in 1988.

Brown contacted local governors and the event has since found success as the town now proclaims itself to be the "Leap Year Capital of the World," hosting people from across the globe.

Of course, this happens once every four years and unlike the soccer World Cup, everyone is a winner, and there's no sign of misfortune in sight.