Monday, February 29 is leap day, a quirky extra day that is squeezed into February every four years in order to keep our calendar operating smoothly. It may seem like a useless day, but without a leap day, the calendar would be off by 5 hours, 48 minutes, and 45 seconds each year. And after 100 years, the seasons would all be off by 25 days! So Leap Day serves an important purpose.