time_t was almost certainly 64-bit on 64-bit archs from the beginning. There's just a lot of 32-bit stuff still out there. And here and there a disk format standarized before people started thinking about the end of time.
Not quite. Until recently llvm’s time_t was an alias to “long”. So a 32b value on 64b windows.
Somehow I thought of FAT.. but UNIX epoch does not make so much sense...
HFS+ uses a different 32-bit timestamp, which is unsigned and starts from 1904-01-01, so it expires on 2040.