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

Georg C. F. Greve greve at
Wed Nov 17 14:58:08 CET 2010

Hi Hendrik,

On Wednesday 17 November 2010 14.04:07 Hendrik Helwich wrote:
> is the second example a valid kolab datetime value? Referring to [1] only
> the  first example should be valid. But both forms hold the same
> information so this is not a problem but maybe a small inconsistency with
> the kolab format specification.

You are right, of course.

But both are examples of timestamps in real existing files I have here.

As both provide Zulu time, but express it differently, the risk is probably 
minimal. But yes, you are right, the format document says that only the first 
is valid while this was written by a reference implementation, which the 
format document also says demonstrates correct behaviour.

So it is an inconsistency, and a reason why I believe we should link this to 
the RFC that everyone else is using for this purpose, as all the operating 
systems that are network capable have built-in functions to read and write 
this format.

> Where are DST information stored? Is this information read from an
> external  source or is it stored inside the kolab format?

DST information should not be stored in the format, because it is subject to 
change. But all operating systems that are capable of running Kolab clients 
have timezone information and libraries available which can provide this 
mapping, and are kept up to date by the distributions themselves, so changes 
would be handled correctly in the future.

The referenced Olson database seems the best and most canonical resource for 
this across all systems that we could find. It is certainly present on all 
GNU/Linux systems, which are the ones that Evolution would be running on.

On my Fedora system, it is located at /usr/share/zoneinfo/

Best regards,

Georg C. F. Greve
Chief Executive Officer

Kolab Systems AG
Zürich, Switzerland

e: greve at
t: +41 78 904 43 33

pgp: 86574ACA Georg C. F. Greve
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