The Romans originally had a 355-day calendar. To keep up with the seasons, an extra 22 or 23-day month was inserted every second year, or so. They were not consistent in adding this month and by Julius Caesar’s time, the seasons no longer occurred at the same calendar periods as in the past. To correct this, Caesar eliminated the extra month and added one or two extra days to the end of various months. Thus extending the calendar to 365 days. He also intended an extra calendar day every fourth year (following the 28th day of Februarius). However, after Caesar’s death in 44 B.C., the calendars were written with an extra day every 3 years instead of every 4 until corrected in 8 A.D. So again, the calendar drifted away from the seasons.
We use the Gregorian calendar to this day. Our year of 365.2425 days, is only off from our solar year by .00031, which amounts to only one day’s error after 4,000 years.
So, you are asking, how did February 29th come to be known as Sadie Hawkins Day? Well, I'll tell you...
Rules of courtship were more strict in years past. Women who were hoping to marry their beaus had to wait for a proposal; they were not allowed to pop the question themselves... except on one day, every four years. You guessed it, on Feb 29!
Sadie Hawkins Day, developed out of the popular cartoon strip "Li' Abner" by Al Capp. In her article in the Baltimore Sun on Feb 29, 1992, writer Sandra Crockett writes- "a female character named 'Sadie Hawkins' who lived in the fictional town Dogpatch was having a tough time getting a man to propose to her. Her father, the mayor of said fictional town, declared one day, 'Sadie Hawkin's' day. The unmarried women in Dogpatch ran -- literally -- after unmarried men to propose that day."
So ladies...it is officially your day!