[tz] User time zones

John Haxby john.haxby at oracle.com
Thu Dec 8 22:32:09 UTC 2011

On 8 Dec 2011, at 18:12, Eric Muller wrote:

> A possible scenario: create an appointment for a time in the future using tzversion1, store the UTC time, and later read the appointment using tzversion2; the time of the appointment may have changed. It is true that in many parts of the world, the likelihood of that scenario is low, but there are others where it's far less uncommon. Also note that the scenario applies equally well to client/server vs. local, one user creating and another reading vs. the same user doing both.

This is exactly why calendaring applications store the time of the appointment along with its timezone.   I have a regular weekly meeting when the clock on the meeting room wall in California says "11am".    Depending on the time of year that's either 7pm or 6pm for me in the UK.

If California decided to change its timezone (to align with Hawaii perhaps) or abandon DST then that meeting would still be guided by that clock on the meeting room wall and not by the time here in the UK. 

The only thing that's not tied to a timezone is an anniversary.   Easter next year, for countries that care, is on 8th April and runs from midnight to midnight regardless of where you are.

This is, of course, what you said!

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