A person born on February 29 may be called a "leapling". In common years they usually celebrate their birthdays on 28 February or 1 March.
For legal purposes, their legal birthdays depend on how different laws count time intervals. In Taiwan, for example, the legal birthday of a leapling is 28 February in common years, so a Taiwanese leapling born on February 29, 1980 would have legally reached 18 years old on February 28, 1998.
In the English speaking world, it is a tradition that women may propose marriage only on leap years. While it has been argued that the tradition was initiated by Saint Patrick or Brigid of Kildare in 5th century Ireland, it 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. Because men felt that put them at too great a risk, the tradition was in some places tightened to restricting female proposals to the modern leap day, 29 February, or to the medieval leap day, 24 February. 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 Denmark, the tradition is that women may propose on leap day 24 February and that refusal must be compensated with 12 pairs of gloves.
In Greece, it is believed that getting married in a leap year is bad luck for the couple. Thus, mainly in the middle of the past century, couples avoided setting a marriage date in a leap year.