Geoff Worboys wrote:

>> Geoff,
>
>> I agree but want to suggest that if it is necessary for a
>> system to commonly convert datetime values between timezones
>> that storing the values as UTC is the only real solution.
> ...
>
> My point is that if you store a timestamp including it's
> time-zone you can have your cake and eat it too!

NO

If you store a meeting as 9AM British Summer Time, and then the meeting
gets moved to the following week - GMT - The there is no way of telling
from the ISO8901 timezone stamp that you need also to adjust an hour!

I got caught last year with all the meetings being displayed an hour out
- and realised that the client browser had change the hour, but there is
no way then of knowing how to correct the display. The simple hour based
timezone provided by the browser is only any use if you do not want to
know about events outside of today.

Saving ISO timestamps with a time is pointless unless you also know the
location that relates to that timestamp. So you may as well store the
daylight saving zone along with the UTC time and then you know how to
display the time - and adjust it if moving a meeting across a daylight
saving boundary.

--
Lester Caine - G8HFL
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