Re: [Tzdist] Fwd: [tzdist] #32 (service): managing historical data

[Cyrus Daboo <[e-mail]>]

Hi Doug,

--On December 11, 2014 at 10:52:55 AM -0700 Doug Royer 
<[e-mail]> wrote:

> If the organizer is responsible for redistribution, then irrelevant or
> out of event time changes do not need to be fetched or recalculated by
> every CUA for every event every time the CUA starts. The organizer simply
> iTIP dispatches on relevant changes only.

And how does an organizer know what is relevant? The organizer has no 
knowledge about which time zone a particular attendee might be in at the 
time of the meeting. If the attendee's time zone changes between when they 
accepted the meeting and the actual meeting time then that change is 
relevant to the attendee, but the organizer has no idea that is the case 
and so will not know to send out an update.

The point is that BOTH the organizer and attendee need to track changes to 
time zones so they can each decide what may or may not be relevant to each 
one of them. When they detect a change that may cause a problem, then yes 
they can use iTIP to communicate appropriate changes to the event. Just 
relying on the organizer to do that is not sufficient.

Note, that even what I describe above is problematic because few, if any, 
calendar clients actually have a concept of what time zone a user is likely 
to be in at some particular point in the future. Most clients allow users 
to change the "view" time zone to view events relative to a specific zone, 
but they don't let you say "next week I will be in London, so use 
Europe/London when viewing any of the days next week). Ultimately clients 
may do something like that if they need to fix these types of problem. (And 
as an aside, the proposed VAVAILABILITY component that is part of the 
calext WG, is one possible way to potentially indicate where one might be 
at some point in the future).

-- 
Cyrus Daboo