Dear lord … a while ago I had to integrate with a client database that had a required “end date” for indefinite events. They filled the value with the maximum year - December 31, 9999.
Our systems initially supported this. But we found an extremely popular and widely used date parsing library has terrible bug. For some reason (if forgot what) as part of its logic it checks something about the date after the date it’s parsing.
So for users of this extremely popular library the 9999 crisis will actually happen a day early.
I kept trying to alter the non responsive maintainers that there was going to be a major crisis with their product in about 7000.
