It fails hard, returning -1 for every call to time(). It doesn’t use a rolling timestamp somewhere in 1901 the way 32-bit Linux applications with 32-bit time_t do. Once Y2038 is reached, the POSIX time() call in a 32-bit app fails with a -1. I know, time_t is 64-bit with pretty much any new Linux distro out there, so why are people seeing Y2038 issues? It’s because the Windows 32-bit POSIX compatibility layer handles Y2038 very poorly. I just spent the last week or so going through the MaraDNS code base and fixing all of the little Y2038 issues.