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

Georg C. F. Greve greve at kolabsys.com
Thu Dec 23 15:59:57 CET 2010

Hi Joon,

My apologies, but I'll need to ask a couple of stupid questions to make sure 
that I fully understand the situation...

On Thursday 23 December 2010 13.19:30 Joon Radley wrote:
> All time in Outlook is stored in UTC. Newer version has a field for time
> zone where they preserve the time zone from iCalendar requests, but from
> what I can see it is never used in calculations.

So they ignore time zone information for calculation?

Just the static information, or also the zone information?

In other words: Can you tell Outlook "this recurrence recurs at this time in 
this time zone?" or do you always need to translate to local first and 
recurrences can only be calculated against the local time zone?

> This cannot be as we just use UTC and Outlook uses the locale information
> to calculate from and to UTC.

If it really did that, recurring events would jump in time in areas with DST, 
as the same time in local time is equal to two different UTC times. So I 
suspect they actually secretly mangle UTC and calculate out the offset between 
DST and standard time for recurring events.

Based on my experience reviewing and debating the time zone issues in OOXML, I 
would even suspect they may accept UTC on the API, but then immediately turn 
it into their proprietary format for further processing, so the calculations 
are not actually UTC based.

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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