Leap years are needed to keep the calendar in alignment with the earth's revolutions around the sun, which take 365 and one-quarter days. Leap day is also added to keep the calendar in line with the seasons.
Up until 1996, February 24 was the designated leap day, or karkauspäivä ("runaway day"), in Finland.
In many countries, leap day has traditionally been a day when women may seize the initiative -- and propose marriage. Finnish custom has its own adaptation of leap day marriage proposals -- should the man turn down the woman's proposal, custom dictates he must buy his suitor cloth for sewing a skirt.