Leap Year was the traditional time that women could propose marriage. In many of today's cultures, it is ok for a woman to propose marriage to a man. Society doesn't look down on such women. However, that hasn't always been the case. When the rules of courtship were stricter, women were only allowed to pop the question on one day every four years. That day was February 29th.

It is believed this tradition was started in 5th century Ireland when St. Bridget complained to St. Patrick about women having to wait for so long for a man to propose. So, according to legend, St. Patrick said the yearning females could propose on this one day in February during the Leap Year.

According to English law, February 29th was ignored and had no legal status. Folks assumed that traditions would also have no status on that day. It was also reasoned that since the leap year day existed to fix a problem in the calendar, it could also be used to fix an old and unjust custom that only let men propose marriage.The first documentation of this practice dates back to 1288, when Scotland passed a law that allowed women to propose marriage to the man of their choice in that year. They also made it law that any man who declined a proposal in a Leap Year must pay a fine. The fine could range from a kiss to payment for a silk dress or a pair of gloves.

Hmmmm, looks like all the single men on the board owe me a kiss or sumpin'
http://marriage.about.com/cs/holidays/a/leapyear.htm