Re: Too late!
"Anything else can be patched by changing time_t to unsigned."
Tried, tested, and proven.
[Open]VMS did that for time_t back in 1998, related to the Y2K kerfuffle. It didn't affect "pure" VMS applications, as VMS has its own rather elegant internal time format, but stuff reliant on time_t (largely but not exclusively C and C-inspired stuff) needed updating.