Re: Diary icalendar tests still broken

> This fixes a bug discussed on emacs-devel; see the thread at
> https://https://lists.gnu.org/archive/html/emacs-devel/2026-07/msg00445.html
>
> The issue was that the library did not distinguish between UTC time and
> times that have an offset of 0 but are not in the UTC time zone,
> e.g. standard times in Europe/London or Europe/Dublin.  This led to test
> failures on systems in these time zones.  This fix represents true UTC
> times by inserting the special value `t' in the zone slot of a decoded
> time at parse time (which `encode-time' already handles correctly).
> This distinguishes them from decoded times with an offset of 0 seconds.

Could you explain why we care about the difference between "0 offset"
and "UTC"?

I understand that we care about the difference between UTC and timezones
which happen to currently have a 0 offset, since those same timezones
may have a non-zero offset at some other moment of the year, but for
a given `decoded-time` object I don't see why it matters (if it did, I'd
expect that we'd want to remember the actual timezone rather than merely
the offset). 


=== Stefan