bug#53396: 27.1; icalendar rendering should include timezone

[Lars Ingebrigtsen <larsi@gnus.org>]

> 2022/1/25 13:00-14:00 Next team meeting
>  Organizer: mailto:user@example.org
> 
> After:
> 
> 2022/1/25 13:00-0500 - 14:00-0500 Next team meeting
>  Organizer: mailto:user@example.org

That looks very confusing, I think -- I first read that as a
mis-formatted time range from 13:00 to 05:00.  

If we want to include the time zone in the display, it shouldn't be
appended to both the start and end times (it's unlikely that they're in
different time zones), and it should be formatted in a different, less
ambiguous way, but I'm not sure how.

And if it's in the local time zone, it probably shouldn't be included at
all.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no