I’ve been reading up on the Y2038 problem and I understand that time_t will eventually revert to the lowest representable negative number because it’ll try to “increment” the sign bit.
According to that Wikipedia page, changing time_t to an unsigned integer cannot be done because it would break programs that handle early dates. (Which makes sense.)
However, I don’t understand why it wasn’t made an unsigned integer in the first place. Why not just store January 1, 1970 as zero rather than some ridiculous negative number?
Because letting it start at signed −2,147,483,648 is equivalent to letting it start at unsigned 0. It doesn’t change the range of a values a 32 bit integer can hold – a 32 bit integer can hold 4,294,967,296 different states. The problem isn’t the starting point, the problem is the maximum value which can be held by the integer. Only way to mitigate the problem is to upgrade to 64 bit integers.
Also (as I just realized that): 1970 was set as 0, so we could reach back in time as well. (reaching back to 1901 seemed to be sufficient at the time). If they went unsigned, the epoch would’ve begun at 1901 to be able to reach back from 1970, and we would have the same problem again.