Re: [PATCH] use UTC instead of GMT

[Natanael Copa <ncopa@alpinelinux.org>]

On Sat, 22 Jul 2017 10:26:25 -0400
Rich Felker <dalias@libc.org> wrote:

> On Sat, Jul 22, 2017 at 11:19:03AM +0200, Natanael Copa wrote:
> > GMT is a timezone officially used by some countries in Europe and
> > Africa. UTC is not a timezone, but a time standard. No country or
> > territory officialy uses UTC as local time.
> > 
> > Also, POSIX mentions UTC a few places[1][2] but never GMT (except as an
> > example[2] for a timezone)
> > 
> > So it makes more sense to use UTC instead of GMT and return UTC when no
> > timezone is set in /etc/localtime or TZ is set to empty.
> > 
> > [1]: http://pubs.opengroup.org/onlinepubs/9699919799/functions/gmtime.html
> > [2]: http://pubs.opengroup.org/onlinepubs/9699919799/functions/timezone.html
> > ---
> > 
> > This causes real problems for people:
> > https://github.com/gliderlabs/docker-alpine/issues/310#issuecomment-316732179
> 
> The motivation for the naming was that POSIX "UTC" is not actually UTC
> but something like UT1 or modified UTC more akin to historical GMT.

Do you have any references on that?

> You can certainly get it to show "UTC" just by setting TZ=UTC, but
> if users are actually hitting problems from this it should be reviewed
> whether the behavior still makes sense.

The problem at hand seems to be that some docker image used hardcoded
timezone to EST so they added automatic tests to verify that timezone
is UTC.

So tests broke on Alpine. To fix that it seems like they set the
timezone via TZ=UTC variable, and that broke things for users who set
the timezone via /etc/localtime.

Basically lot of minor fuzz, which all can easily be worked around, but
its just annoying.

I checked what FreeBSD, OpenBSD and GNU/Linux does when timezone is
unset. Seems that they all use "UTC" so I think that makes most sense.



> 
> Rich