timezones, question of

Helge Hess helge.hess at opengroupware.org
Fri Feb 6 02:33:41 CET 2009

On 05.02.2009, at 10:36, Bernhard Reiter wrote:
> Unfortunately Helge is right in that there is a problem with  
> recurrences,
> daylight shifting and timezones. Currently each client will use their
> understanding of daylight shifting and this does not work for some  
> cases.

I'm not sure I can follow you. It does work in _no_ case for  
recurrences which span timezones with different DST rules?! Eg the  
super simple case, USA recurrences displayed in Europe, does not work  
properly at all.

BTW: AFAIK the most difficult case is Brazil, where the DST shifts are  
redeclared _every_ year. Hence you can't even convert a date like

   2011-03-06 16:00 BRT

to UTC. It will only be decided in 2010 whether that will be 13:00 or  
14:00 UTC.
Even iCalendar can't deal with it ... (since TZID must point to a  
VTIMEZONE, which in turn must contain the tz rule).

Timezones are lovely, aren't they? ;-)

Helge Hess

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