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

[Joon Radley]

Hi Georg,

Let me start off by giving some background.

Time zone information only appears in appointments.

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

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

> 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

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.

> 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.

Storage is in UTC then they do there calculations from there.

Notes:
1) Outlook does not use the Olson database naming conventions. (AFAIK there is no one to one mapping for this).
2) Outlook does not use the Olson database for getting its time zone information. This should in theory be the same, but making it a MUST requirement will make all Outlook clients non complying.
3) The time zone information can be altered, by Outlook, in a way (view point) outside the intended or MUST requirements of KEP2.
4) Non event objects do not store time zone information. (Still have to check on the task recurrence.)
5) Making KEP2 strict will drop support for Outlook 2003.

Best Regards

Joon Radley

Cell: +27 (0)83 368 8557
Fax: +27 (0)86 547 2353
E-mail: support at toltec.co.za
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On 23 Dec 2010, at 4:59 PM, Georg C. F. Greve wrote:

> 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
> 
> 
> -- 
> 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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