https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114645
--- Comment #17 from Jonathan Wakely <redi at gcc dot gnu.org> --- And "Factory" isn't a valid POSIX zone, so remove that one from the list. So if I'm reading it correctly, some European zones and the US zones can be used in $TZ with libc++ but most IANA zones won't work. And then it just silently ignores $TZ and falls back to /etc/localtime so an application still can't actually rely on $TZ being used. It might work, for a small set of zones, or it might not work.
