Recurring events with timezone
h.helwich at tarent.de
Wed Oct 20 09:34:07 CEST 2010
Am 20.10.2010 08:46, schrieb Joon Radley:
> Hi Hendrik,
> This is an excellent example. Your argument is that the incorrect conversion in the client of UTC -> local time can be fixed by adding time zone information to the object.
> Lets run a use case with this. User A is the creator of the object and is situated in Johannesburg. User B that shares the folder is situated in Germany (for the daylight savings time).
> The problem is: UTC -> User B local time is incorrect.
> Your suggested solution is: User A Time Zone + User A Local Time -> UTC -> User B local time
> UTC -> User B local time conversion will still be broken, as you need User B TZ to fix the incorrect calculation. Thus by adding the User A TZ information to the object no problem is solved.
> The only time when the TZ information will help is when User A and User B is in the same time zone and they both know it. All other user cases do not benefit from User A’s TZ information.
> You are trying to fix a client “bug” by providing it with information, which will only be valid/helpful in very limited cases.
> By fixing the UTC-> locale conversion you will fix all the use cases. The localtime function has never failed me. Is there a problem with it on your OS?
timzones are working fine on my OS :-) the UTC time can surely be used
for single events/tasks. But it is possible to code recurring events in
kolab so you must add timezones to the format even if they are complex.
This is obvious i think. Otherwise it is not possible to fix this problem.
To the example:
The correct way would be to make the kolab xml with timezone e.g. like this:
<?xml version="1.0" encoding="UTF-8"?>
<product-id>KOrganizer 3.5.9 (enterprise35 20100805.1161816), Kolab
<recurrence cycle="monthly" type="daynumber">
(I added the timezone block and changed start-date and end-date to the
My Kontact now can see that i am in the same time zone as it is stored
in the event and does not need to convert the local times. It can show
me the 10 o'clock start-time for all the year. It also can do the stored
local -> UTC -> local conversion but this would be an identity function
and will cause the same result.
If i am in Johannesburg my Kontact can convert each start-time to the
UTC time by using the stored time zone from germany and then convert it
to the system local time.
german local 10 -> UTC 8 -> south africa local 10
german local 10 -> UTC 9 -> south africa local 11
So this example could be calculated correctly. Without storing the time
zone information of germany that could not be possible.
More information about the format