> time_t is now 64 bits on all platforms.

Linux[2]:

> The vast majority of 64-bit hosts use 64-bit time_t. This includes GNU/Linux, the BSDs, HP-UX, Microsoft Windows, Solaris, and probably others. There are one or two holdouts (Tru64 comes to mind) but they're a clear minority.

This is little help for older, already deployed systems, of course.

[1]: https://www.openbsd.org/55.html

[2]: https://mm.icann.org/pipermail/tz/2004-June/012483.html