Will You Marry Me?

From Wikipedia:

There is a tradition, said to go back to Saint Patrick and Brigid of Kildare in 5th century Ireland, but apparently not attested before the 19th century, whereby women may make marriage proposals only in leap years.

Supposedly (but disputed), in a 1288 law by Queen Margaret of Scotland (then age five and living in Norway), fines were levied if the 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.