Leap Day

February 29 is a leap day (or “leap year day”), an intercalary date added periodically to create leap years in the Julian and Gregorian calendars. It is the 60th day of a leap year in both calendars, and 306 days remain until the end of the leap year. It is also the last day of February in leap years with the exception of 1712 in Sweden. It is also the last day of meteorological winter in the Northern Hemisphere and the last day of meteorological summer in the Southern Hemisphere in leap years.

https://en.wikipedia.org/wiki/February_29