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

[Soren Stoutner]

On Wednesday, October 8, 2025 2:15:53 PM Mountain Standard Time Vagrant 
Cascadian wrote:
> We can test consitent timezones, rather than relying on timezones that
> may or may not have daylight savings time such that a package might
> build reproducibly with or without daylight savings time.
> 
> Even if we can find sufficiently divergent timezones that happen to not
> have daylight savings time today, there is no guarantee that that a
> particular Continent/City will not institute daylight savings time at a
> later date, or even change timezone entirely.
> 
> Using UTC offsets avoids all of that mess.
> 
> It also allows us to make sure at least the day changes, by having
> offsets spanning over 24 hours (e.g. UTC+12 and UTC-14 ~= 26 hour time
> difference, and which is actually represented in the real world due to
> countries that span the international date line).

Using consistent and divergent timezones that do not implement daylight 
savings time is indeed an important consideration.  I think that is fully 
addressed by using the Etc/GMT+12 and Etc/GMT-14 syntax.

Please note, as described in the original bug report:

“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


On Wednesday, October 8, 2025 1:41:17 PM Mountain Standard Time Guillem Jover 
wrote:
> As was mentioned on the list thread, this change would require for tzdata
> to be installed everywhere, otherwise the results are bogus (AFAIUI).

There may be some great difficulty caused by making tzdata a dependency of 
reprotest.  If there is I would be interested in know what it is.

It should be noted that the reproducible builds project successfully builds 
this package.

https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/
pyinstaller-hooks-contrib.html

My memory is that didn’t used to be the case.  So, either my memory is wrong 
or reproducible builds recently started using the Continent/City (zoneinfo) 
syntax.  In either case, I think it would be advantageous for reprotest (and 
the Salsa CI test that uses it) to mirror the behavior of reproducible builds.

-- 
Soren Stoutner
soren at debian.org
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