February 29: Leap day
February 29, also known as leap day in the Gregorian calendar, is a date occurring in most years evenly divisible by 4 (2004, 2008, 2012, and 2016). Years evenly divisible by 100 don’t contain a leap day, with the exception of years that are evenly divisible by 400, which do contain a leap day. Therefore 1900 didn’t contain a leap day while 2000 did. Years containing a leap day are called leap years. February 29 is the 60th day of the Gregorian calendar in such a year, with 306 days remaining until the end of that year.
