Original: February 29 in the Gregorian calendar, the most widely used today, is a date that occurs only once every four years, in years evenly divisible by 4, such as 1996, 2000, 2004, 2008, 2012 or 2016 (with the exception of century years not divisible by 400, such as 1900).
Simplified: This date only occurs every four years, in years that can be exactly divided by 4, such as 1988, 1996, or 2008, except century years that can not be divided by 400 without leaving a remainder, such as 1900.