The surprising struggle to get a UNIX Epoch time from a UTC string in C or C++

from blog Bert Hubert's writings, | ↗ original
So how hard could it be. As input we have something like Fri, 17 Jan 2025 06:07:07 in UTC, and we’d like to turn this into 1737094027, the notional (but not actual) number of seconds that have passed since 1970-01-01 00:00:00 UTC. Trying to figure this out led me to discover many ‘surprise features’ and otherwise unexpected behaviour of POSIX...