Leap Day on Feb. 29 is also considered by many to be Sadie Hawkins Day, an observance that originated from Al Capp's classic pen and ink comic strip, "Li'l Abner," in which the character of Sadie Hawkins grew desperate to marry and called unmarried men to court her on Sadie Hawkins Day. Sadie Hawkins Day is recognized as an American folk event in which girls take the initiative to ask a boy out for a date, which was something unheard when the practice originated after the Great Depression. 

This observance of women turning the typical stakes around for dating only comes around once every four years for many observers.

The Sadie Hawkins' character hit the U.S. pop scene in 1937, according to Time magazine. In the comic, Hawkins was a spinster at the age of 35, so her father set up a race for local bachelors in the town of Dogpatch. Whoever Sadie caught was going to be her husband. The town, and the reading audience, loved the idea and the race became an annual fixture of the comic strip, and soon spread into real-life society, spawning Sadie Hawkins Day dances.

Capp held his fictional race in November, around election time, but he may have lifted it in part from the Brits, who have held for centuries that women may propose marriage during leap years, reports St. Augustine Record.

In U.S. traditions, the Leap Day phenomenon has been observed at least since the early 20th century. Slate has a slideshow of daffy vintage postcards dedicated to warning men about the hazards of accepting female visitors on Leap Day.

In Finland, if a man refuses a woman's proposal on Leap Day, he apparently must buy her fabric for her skirts.

February 29 is significant for women, according to women's issues' experts, thanks to an old Irish tradition called St. Bridget's Complaint, which granted women permission to propose marriage on that day.

According to the Li'l Abner website, Sadie Hawkins Day is an unspecified date in November which Al Capp observed in his comic strip for four decades.

Capp, who lived from 1909 to 1979, was regarded by many as the creator of the greatest comic strip of all time. He was born Alfred Gerald Caplin in New Haven, Conn. After nearly 20 years of prominent bachelorhood, Li'l Abner finally married Daisy Mae in 1952, an event that shocked the country and made front page news.

Capp was a frequent and outspoken guest on the "Tonight" show, spanning hosts Jack Paar, Steve Allen and Johnny Carson. He authored his own newspaper column and radio show, and was a guest lecturer at campuses nationwide. Capp retired the strip in 1977 and died two years later. Capp's "Li'l Abner" stands the test of time as a pinnacle of cartoon art and social satire. Li'l Abner inspired a long-running Broadway musical in 1957, as well as  two film adaptations.