This type of year is also known as a bissextile year
... by the insertion 
of leap seconds into Coordinated Universal Time (UTC), owing to the variability 
of... [DOC] [TLE] Next Leap Day: February 29, 2020 - Timeanddate.com [PAR] A Leap Year consists of 366 days  not 365  where February 29 is added as ... 
At the time, leap day was February 24, and February was the last month of the 
year.