Thank you, Robert, for the explanation! I asked because I was using Hypothesis to generate test data for a function I had written, and some of the generated test data contained the prefixes: https://hypothesis.readthedocs.io/en/latest/data.html#hypothesis.strategies.... In one particular instance some function runs failed with these prefixed timezones, and it turned out that the host which ran the tests did not have these timezones installed. That’s how I stumbled upon these prefixes… and then wasn’t able to find them documented. So, I appreciate your sharing some information, thank you! This raises an interesting point, though: suppose I receive a “genuine UTC” timestamp (i.e. produced on a machine with right/UTC timezone) and then I read that timestamp on a POSIX machine (i.e. with posix/UTC or just UTC timezone) — there is a slim chance that my timestamp has now shifted by one second, correct? And could that be exploited 🤔 With many greetings, Jens PS: Is there a public link available to this email thread?
On Jan 18, 2023, at 04:57, Robert Elz <kre@munnari.OZ.AU> wrote:
Date: Sun, 15 Jan 2023 18:40:27 +0100 From: =?utf-8?Q?Jens_Tr=C3=B6ger?= via tz <tz@iana.org> Message-ID: <2FB37B4F-3F85-4260-8C49-D770591075C6@light-speed.de>
| Today I stumbled upon timezone strings like “right/UTC”,
Many systems don't bother installing those, as they're not usually very useful on POSIX systems.
| I’m unable to find details on the meaning & classification of the | “right/” here and how it relates to actual UTC and other timezones.
The right/* zones convert genuine UTC (that is, the time that occasionally steps 23:59:58 23:59:59 23:59:60 00:00:00 00:00:01) with leap seconds counted.
That's not what you get in a posix time_t - there all days are 86400 seconds long, no matter what, so a year is always (365 or 366) * 86400 seconds.
Only if you get (from somewhere) timestamps that are genuinely in UTC and not the POSIX approximation of it you get from gettimeofday() or clock_*() or stat(), ... are the right/* zones useful for anything at all. Unless you're an astronomer, or rocket engineer, the chances of that aren't high.
kre
-- Jens Tröger https://savage.light-speed.de/