Recurring events with timezone

Andrew McMillan andrew at morphoss.com
Wed Oct 27 21:38:35 CEST 2010


On Wed, 2010-10-27 at 14:49 +0200, Joon Radley wrote:
> 
> > Sure, I live in New Zealand, but the teleconference is scheduled
> > according to a New York time, where other parties on the conference call
> > live, rather than where I live.
> > 
> > Other people on the call live in Europe, some in South America, a few in
> > Australia, but we had to pick *some* timezone and the boss lives in New
> > York and he likes to fit the meeting in between his regular lunch
> > appointment and his regular Tuesday 10:30 meeting with the finance
> > committee.
> 
> Again, if I am in South Africa, what do I care what time zone you
> scheduled it for, I just need to know what time of the night I need to
> get up for the call.

If you don't know the DST rules for the timezone the event is scheduled
in, how are you supposed to know what UTC time this instance of the
event is scheduled for?

Certainly if the event is at an invariant UTC time conversion of that to
my localtime is easy, but I'm talking about an event which is in someone
*else's* local time (not mine) and I want to know when repeat
occurrences will be in *my* local time, after we've crossed a couple of
DST boundaries.

If you only store the UTC event then how do you get invariant local
times?  Do meetings shift by one hour when you cross a DST boundary? If
not then you are (in effect) calculating the instance time according to
that DST rule.  I have events which are calculated in such a manner,
where the DST rule that applies to calculating the UTC time is *not*
*mine*.  And I don't get to choose that DST, it's arbitrarily handed
down by someone else.

Now OK, by applying DST rule A I can calculate the UTC instance times,
but having done so I now want to apply DST B to convert these instance
times (a second conversion) to *my* timezone.

Without knowing which timezone "A" was, I cannot do this double
conversion, and so I miss my meeting by one or two hours.  The solution
to this problem *requires* knowing two timezones: the one which defines
the scheduling rules, and my local timezone.  You seem to be suggesting
that through some unexplained magic you can calculate the event just
according to your local timezone.


Regards,
					Andrew.

-- 
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andrew (AT) morphoss (DOT) com                            +64(272)DEBIAN
            Nothing succeeds like the appearance of success.
                          -- Christopher Lascl

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