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List:       kde-pim
Subject:    Re: [Kde-pim] Re: [kdepim-users] times wrong in korganizer
From:       Reinhold Kainhofer <reinhold () kainhofer ! com>
Date:       2005-03-24 21:05:18
Message-ID: 200503242205.19936.reinhold () kainhofer ! com
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Am Donnerstag, 24. März 2005 21:36 schrieb Allen Winter:
> I finished making all the changes necessary to make kdepim compile with the
> new Calendar constructor that requires a timezoneId (by default I used
> UTC). 

Good!

> Remember that the only purpose for the timezoneId AFAIK is to determine
> which timezone you want to view Incidences in. 

Nope, the time in memory are in local time (e.g. if you add a new event), so 
the tz needs to be used to determine how much you need to shift the times to 
UTC. 
But I guess this is just a different view of things. Currently, it's really 
just a property of the view. As mentioned below, recurring events really 
depend on the time zone they are in:
E.g. an event recurring every monday at 1:00 CEST (UTC+2:00) does not recur 
every monday when viewed in e.g. Eastern time (where the event recurs at 
19:00 on Sunday). So, recurrence rules heavily depend on the timezone, too!


> Incidence storage should 
> always be UTC or no timezone (i.e. floating)

With libical 0.24 we can finally also save times with a specific tz attached:

DTSTART;TZID="HelsinkiTime":20030818T100000
DTEND;TZID="HelsinkiTime":20030818T113000

The exact specification of the daylight-saving shift is then given in a 
separate VTIMEZONE object in the .ics file:

BEGIN:VTIMEZONE
TZID:"HelsinkiTime"
BEGIN:DAYLIGHT
TZOFFSETFROM:+0200
TZOFFSETTO:+0300
TZNAME:EEST
DTSTART:19700329T030000
RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=-1SU;BYMONTH=3
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0300
TZOFFSETTO:+0200
TZNAME:EET
DTSTART:19701025T040000
RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=-1SU;BYMONTH=10
END:STANDARD
END:VTIMEZONE

Currently, libkcal can only read these ones, but cannot write them out, which 
is sub-optimal and the cause of bugs like 
(http://bugs.kde.org/show_bug.cgi?id=76158). Sooner or later, libkcal needs 
support for this, but right now we should at least keep in mind that in the 
future the correct tzid will be more important (and then it will not be taken 
from the entries in /usr/share/zoneinfo, but from .ics snipplets in libical's 
data dir).

> We really need to get this right once and for all.

Definitly.

Cheers,
Reinhold


-- 
------------------------------------------------------------------
Reinhold Kainhofer, Vienna, Austria
email: reinhold@kainhofer.com, http://reinhold.kainhofer.com/
 * Financial and Actuarial Mathematics, TU Wien, http://www.fam.tuwien.ac.at
 * K Desktop Environment, http://www.kde.org/, KOrganizer / KPilot maintainer

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