I had to check in case it had actually ever occurred, since I had recently read about 30 February existing for reals: https://www.timeanddate.com/date/february-

I had to check in case it had actually ever occurred, since I had recently read about 30 February existing for reals: https://www.timeanddate.com/date/february-30.html https://www.timeanddate.com/date/february-30.html It looks like there has never been a real 31 February.