Recurring events with timezone
Tobias König
tobias.koenig at kdab.com
Thu Oct 28 18:47:24 CEST 2010
On Thursday 28 October 2010 16:20:15 Georg C. F. Greve wrote:
> Hi Tobias,
Hej Georg,
> > Either the client, which creates the recurring event, splits the event
> > up in two recurring events, one for each DST mode. Then during
> > summertime a recurring event with 08:00 UTC is used and during winter
> > one with 07:00 UTC.
>
> How would that work?
I'm not familiar with the recurrence rules of the kolab format, but with ICal
one can specify quite sophisticated exceptions. So a german kolab client could
split the above event into the two events:
- recur on every day on 08:00 UTC from last sunday in march till last sunday
in october
and
- recur on every day on 07:00 UTC from last sunday in october till last
sunday in march
(where 'last sunday in xyz' might be literal date values)
So only the client, which is creating this event, has to know about the
specifics of this DST. All other clients see fixed UTC values where they just
add their current DST offset.
The question is how complex these DST rules are in the various country and if
kolab format supports to express them as exceptions.
> And how would the clients know against which DST zone to adjust their local
> time, e.g. how does the Brazilian client know that it is supposed to take
> 07:00 UTC / 08:00 UTC based on the German DST zone?
The other clients (not the creator) just add their local DST offset to get the
local time. The time of the event is bound to the creators timezone, right? So
the local time for the other clients changes.
The Brazilian client would not have to care about German DST. It just shows
the event which is currently 'active'. So from march till october the 08:00
UTC event will be listed with the current Brazilian DST added and from october
till march the 07:00 UTC will be listed with the current Brazilian DST added.
> As you are part of the Kontact side of things, which is the approach that
> would work best for the KDE PIM environment?
I'm not working on the calendaring part, so I can't really comment on what
would fit best. But since we have a good timezone/date library, both
conversions should be possible for us.
Ciao,
Tobias
--
Tobias Koenig | tobias.koenig at kdab.com
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel. Germany +49-30-521325470, Sweden (HQ) +46-563-540090
KDAB - Qt Experts - Platform-independent software solutions
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