UPDATE: KEP 2: Modification of datetime: store local time, add 'tz' attribute (revision #10743)

Georg C. F. Greve greve at kolabsys.com
Thu Jan 6 16:59:23 CET 2011

Hi Joon,

On Sunday 26 December 2010 09.38:03 Joon Radley wrote: 
> Let me start off by giving some background.

Thanks a lot for this, quite helpful to start understanding Outlook better.

> In Outlook 2003 and older Outlook included a static time zone structure
> only in recurring appointments.

Is that static time zone structure part of the event? If so, it should be 
possible for the plugin to generate that from the Olson database, no?

> In Outlook 2007 and later Outlook include rule based time zone information
> that look very similar to the Olson rules.

Alright. So here it seems to take much of the same route.

Naturally Microsoft remains incompatible to everything else with its 
conventions, but fortunately there is a mapping through the Unicode Common 
Locale Data Repository (CLDR) and the KEP includes a mapping between the 
location identifiers that should make this fairly simple for you.

> Time is stored in UTC the the calculation is made against time zone
> information relevant to version of Outlook. We can only provide the zone
> information, but cannot control how it is calculated.

As mentioned before, it is pretty much impossible that Outlook actually 
calculates this from UTC, as that would necessarily mean unstable events in 
local timezones with DST.

Can you maybe feed it some data for me to understand what it actually does?

Try giving it the Europe/Berlin timezone (whichever that is in Windows) and 
then feed it once 9:00 UTC and another time 10:00 UTC for a weekly recurring 
event, and let me know where the event lands in week 52 and week 25, 

Best regards,

Georg C. F. Greve
Chief Executive Officer

Kolab Systems AG
Zürich, Switzerland

e: greve at kolabsys.com
t: +41 78 904 43 33
w: http://kolabsys.com

pgp: 86574ACA Georg C. F. Greve
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