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

[Georg C. F. Greve]

Hi Joon,

On Sunday 26 December 2010 09.55:07 Joon Radley wrote:
> This is what I would suggest.
> 1) All timestamps are stored in UTC in the RFC3999 Zulu format without
> micro seconds. (The current format). 2) Inclusion of a tz structure in
> event objects.
> 2.a) NON-DST zone (Only gives offset from UTC)
> 2.b) DST Zone (gives rules for DST start/end with bias and time offsets.
> Can be one or more rules) 3) 2 contains a non fixed text representation of
> the zone name. This is just used for displaying information. 4) The tz tag
> must be a root tagged. This will ensure that the tag is always preserved.
> 5) Together with a tag and the format version number the storage format
> can indicate that tz field was used in calculating the the timestamps.

This is a lot of information to store in order to be able to recreate the 
intended local time and then calculate the rest from there.

Also some parts of this are still ambiguous, e.g. is 1) stored against DST or 
non-DST? 2) seems to be doing static encoding again, which we know is a 
solution that does not work very well in practice, and 3) will ensure that a 
client does not understand the time zone information, so when a user wants to 
change the time zone, we'll be faced with issues of trying to translate from 
an unknown timezone to one that would be unknown to others.

So this seems a lot more complex (and consequently error prone) than storing 
local time, from which all of the above can easily and reliably be generated 
should you require it for Outlook.

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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