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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/114645] std::chrono::current_zone ignores $TZ on
 Linux
Date: Mon, 08 Apr 2024 20:48:09 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114645

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The libc time zone doesn't necessarily correspond to anything in the IANA
database anyway. If you use a POSIX time zone definition like TZ=3D"abc4abd=
" then
libc will use that to generate a custom time zone and use that for localtim=
e,
ctime etc.

That's not compatible with the std::chrono model, which uses the IANA zones=
. So
"the time zone libc would consider local" might not be a real time zone any=
way.

If you want to interpret $TZ then you can write code to do so, and convert =
that
into a name that std::chrono::locale_zone understands. So if TZ is an IANA
name, use it directly, otherwise extract the offset part and then use somet=
hing
like "Etc/GMT-8".=