Thanks, Julie!

Feb. 29, 45 B.C.: Julius Caesar Takes the Leap

45 B.C.: Roman dictator-for-life Julius Caesar, alarmed that the calendar is growing out of whack with the seasons, adds an extra day to the month of February every four years.

The new Julian leap day wasn't added at the end of February originally, but on the day preceding the 6th of the calends of March. The Romans didn't count the days of the months from 1 on up, but used an idiosyncratic system of calends, nons and ides -- and we all know what happened to ol' J.C. on the ides of March, 44 B.C.