[tz] Unexpected footer in Africa/Casablanca

Paul Eggert eggert at cs.ucla.edu
Mon Jan 10 20:46:03 UTC 2022

On 1/10/22 08:55, Almaz Mingaleev wrote:

> I was investigating generated TZif files and the generated footer for 
> Africa/Casablanca is "XXX-2<+01>-1,0/0,J365/23". Is that expected?
> Effectively it behaves like GMT+1, but SAVE is -1:00 even though it is 
> 1:00 in rearguard.zi. How do I instruct zic to generate plain "<+01>-1" 
> or skip it at all?

One fix is to change ziguard.awk to generate a rearguard-format .zi file 
that has a more-natural transition for Morocco in May 2087. ("More- 
natural" from the rearguard viewpoint that is; it's more-awkward from a 
real-world viewpoint.) Proposed patch attached; it causes the string to 
be "<+01>-1" for rearguard format too. Thanks for reporting the glitch.

> I believe I am doing something wrong, as in MacOs it is empty and 
> "<+01>-1" in Linux, but I can't figure out what command options I should 
> specify in zic.

It's "<+01>-1" on GNU/Linux platforms like Ubuntu and Fedora that use 
the default format. These distros are not using rearguard-format TZif 
files and so don't have rearguard issues there.

I'm not sure why it's empty in macOS. macOS 12.1's 'zic --version' 
reports "zic: @(#)zic.c 8.22" which corresponds to tzcode2010m, so 
perhaps it's merely because macOS is stuck on a tzcode version that is 
so old that you can't easily tell that macOS is using rearguard format. 
(macOS's zdump doesn't seem to work past the year 2038, and Apple should 
upgrade well before that year rolls around.)

While we're on the subject, what is Android's current state of support 
for negative DST and for timestamps past 2038? On the GNU/Linux side, I 
expect most distros support both - the stragglers being old-fashioned 
32-bit x86 and ARM distros, where 64-bit timestamps weren't supported 
until Linux 5.6 (2020-03-29) and glibc 2.34 (2021-08-02), and even now 
many apps haven't been updated yet.
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