leap day
February gets an extra (29th) day! You only get to see this day every 4 years, when the year is divisible by 4. However, if the year is divisible by 100 but not 400, it won't have a February 29th. Years 2000 and 1600 are leap years which have a February 29th, but the year 1900 isn't. The next leap day will be February 29th, 2028.