bug#67706: 30.0.50; timer-next-integral-multiple-of-time does not account for different time-zones

[Bruno Boal <egomet@bboal.com>]

Eli Zaretskii <eliz@gnu.org> writes:

>> Cc: info@protesilaos.com
>> From: Bruno Boal <egomet@bboal.com>
>> Date: Fri, 08 Dec 2023 11:51:01 +0000
>> 
>> While trying the following snippet in both Lisbon and Athens, we
>> get the same timer object as showed in list-timers.
>> 
>> (run-at-time t 14400 #'message "Testing")
>> 
>> What we would expect, is two different timer objects accounting for the
>> different time zones.
>> 
>> We did a edebug and found out that the function aforementioned on the
>> subject is always returning the same value despite of the different
>> local times.
>> 
>> Are we missing something obvious or is this a bug?
>
> Please show a minimal recipe, starting from "emacs -Q", to reproduce
> the issue you are seeing.  I'm not sure I understand all the details,
> and therefore don't follow why you expected two objects.

Let me try to demonstrate the possible issue.

Running the following snippet in my PC, with Lisbon time of 16h36:

     (run-at-time t 14400 #'message "Testing")

Checking result of `list-timers' function:

Next           Repeat      Function
3h 24m 34.7s       4h      message

Running the same snippet in Prot's PC, with Athens time of 18h36:

     (run-at-time t 14400 #'message "Testing")

Checking result of `list-timers' function:

Next           Repeat      Function
3h 24m 34.7s       4h      message

So despite the difference of time-zones the next occurrence of Function
has the same Next time interval. Is this the expected behavior? Because
reading the documentation I would expect the Function to have a Next
interval multiple of Repeat in order to run at 20h local time of the
machine where the code was evaluated. Being this the case, the Next
value in Prot's PC would have to be 1h 24m34.7s.

Hope I've made my question clearer.
Thanks.

> Thanks.