[Users] claws-mail displays ics file wrongly

[David Fletcher]

>From: clawsmail at pasdzierny.de
>hello,
>
>I am not an expert in ics files, but the attached ics file should
>refer to 10h CEST (and it does so when imported into google calendar)
>but I get 12h displayed using claws-mail (version 4.3.0 )(HTML was
>turned off), see attached screenshot as pdf
>
>Because of the difference of 2h is the same as the difference from CEST
>to UTC my guess is that the timezone is considered falsely or not at
>all.
>
>cheers, Martin.


I think there's something strange about this ICS calendar file.

Germany is 1 hour ahead of United Kingdom. Opening it in the UK it shows
a meeting at 11am (UK time) in Claws, so that is two hours the wrong
way. If I open it using the Apple calendar it shows a meeting at 10am
(UK time), so that is one hour wrong.

If it's meant to be 10am CEST there's something wrong with the ICS file
as it should show 9am (UK), not 10 or 11. Central European Summer Time
is 1 hour ahead of United Kingdom.

Looking inside the file it has 8 different time-zone offset entries as
pairs of

TZOFFSETFROM:
TZOFFSETTO:

I would guess that wherever this came from has tried to supply
pre-calculated times for a range of regions, and this over-supply of
information is confusing not just Claws but also the Apple calendar too.

Looking inside the ICS file shows a product name "Kommunix GmbH//iCal4j
1.0//DE". Searching Google for this takes me to a github page:
https://github.com/ical4j/ical4j/issues

Looking quickly (not in-depth) at the issues listed there, it has
multiple complaints about the timezone information for various regions
being wrong. Maybe this is the issue, not Claws Mail! Maybe the ICS file
is theoretically correct, but actually too complicated for some
calendars (including the Apple one) to interpret.

Best regards, David.