Bug#1117626: reprotest: Use the Continent/City (zoneinfo) syntax for time zone variation

[Soren Stoutner]

Package: reprotest
Severity: normal

I maintain pyinstaller-hooks-contrib, which includes a test (run during build
and in autopkgtests) that parses the system timezone.  This test currently
fails Salsa CI reprotest and other reproducibility tests because they modify
the timezone in the build environment using syntax like GMT+12 instead of the
Continent/City (zoneinfo) syntax.

zoneinfo._common.ZoneInfoNotFoundError: 'tzlocal() does not support non-
zoneinfo timezones like GMT+12. Please use a timezone in the form of
Continent/City’

https://salsa.debian.org/python-team/packages/pyinstaller-hooks-contrib/-/jobs/8382666#L6097

I can see the wisdom in having reproducibility tests check to make sure that
packages build correctly in different timezones.  My question is:  do we gain
anything by using the GMT+12 syntax, or could we achieve the same results by
varying the timezone using the Continent/City format?

This was discussed on debian-devel in the thread beginning at:

https://lists.debian.org/debian-devel/2025/10/msg00006.html

Etc/GMT+12 and Etc/GMT-14 would provide the largest offset (note the
 difference in the numbers, with the positive offset going up to 12 and the
 negative offset going up to 14).

https://en.wikipedia.org/wiki/List_of_tz_database_time_zones#List

"The special area of "Etc" is used for some administrative zones, particularly
for "Etc/UTC" which represents Coordinated Universal Time. In order to conform
with the POSIX style, those zone names beginning with "Etc/GMT" have their sign
reversed from the standard ISO 8601 convention. In the "Etc" area, zones west of
GMT have a positive sign and those east have a negative sign in their name (e.g
 "Etc/GMT-14" is 14 hours ahead of GMT).

https://en.wikipedia.org/wiki/Tz_database#Area