KEP 2: Modification of datetime type, introduction of 'tz' sub-tag

Gunnar Wrobel wrobel at
Tue Nov 23 14:29:46 CET 2010

Hi Georg,

Zitat von "Georg C. F. Greve" <greve at>:

> On Wednesday 17 November 2010 12.33:58 Jeroen van Meeuwen (Kolab Systems)
> wrote:
>> - Does the nesting make the new version of the format incompatible with
>> older  clients?
> Provided the clients are Kolab compliant, i.e. preserve unknown tags, and use
> proper XML parsing, it should not be.

I know from experience that we cannot rely on that. It is some time  
ago when I did cross-client testing but I'm certain that not all  
clients kept their fingers from the entries of other clients.

For the Kolab_Format PHP library this only holds for additional tags  
on the base level but not for subtags. The current library would  
definitely kill the <tz> tag.

Probably no major disaster as everything that uses Kolab_Format is  
linked to the server release anyway.



>> - Is there a specific reason the <tz /> element is nested in the
>> <start-date  /> element? Do we expect to see end-dates specified for a
>> different timezone?
> Most clients allow to choose the time zone for each of the time  
> fields that is
> entered. So not being able to model that in storage would impose much larger
> changes upon clients in their user interaction, or an implicit decision which
> explicit user input to discard, whereas a nested value will avoid  
> placing that
> burden on the client implementor or user.
> At the same time, there is no additional cost to doing this nested, and it
> makes sure that we can cover future use cases that we may not be aware of
> right now without having to modify the format for them.
> Best regards,
> Georg
> --
> Georg C. F. Greve
> Chief Executive Officer
> Kolab Systems AG
> Zürich, Switzerland
> e: greve at
> t: +41 78 904 43 33
> w:
> pgp: 86574ACA Georg C. F. Greve

Gunnar Wrobel
Developer, Kolab Systems AG

e: wrobel at
t: +49 700 6245 0000

pgp: 9703 43BE

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