In the Gregorian calendar, the current standard calendar in most of the world, most years that are evenly divisible by four are leap years. In each leap year, the month of February has 29 days instead of 28. Adding an extra day to the calendar every four years compensates for the fact that a period of 365 days is shorter than a solar year by almost six hours.
Leap Years benefit from many folk customs. In the United States Leap year has also become (unofficially) known as Sadie Hawkins Day. Sadie Hawkins Day is a pseudo-holiday that originated in Al Capp's 1934–1978 comic strip, Li'l Abner, which inspired real-world Sadie Hawkins dances, where girls ask boys out.
In the British Isles, it is a tradition that women may propose marriage only on leap years. While it has been claimed that the tradition was initiated by St. Patrick or Brigid of Kildare in 5th century Ireland, this is dubious, as the tradition has not been attested before the 19th century.
Supposedly, a 1288 law by Queen Margaret of Scotland (then age five and living in Norway), required that fines be levied if a marriage proposal was refused by the man; compensation ranged from a kiss to £1 to a silk gown, in order to soften the blow.
According to Felten: "A play from the turn of the 17th century, 'The Maydes Metamorphosis,' has it that 'this is leape year/women wear breeches.' A few hundred years later, breeches wouldn't do at all: Women looking to take advantage of their opportunity to pitch woo were expected to wear a scarlet petticoat—fair warning, if you will."
In Finland, the tradition is that if a man refuses a woman's proposal on leap day, he should buy her the fabrics for a skirt.
In Greece, marriage in a leap year is considered unlucky. One in five engaged couples in Greece will plan to avoid getting married in a leap year.