Recurring events with timezone

Andrew McMillan andrew at
Thu Oct 21 04:02:01 CEST 2010

On Wed, 2010-10-20 at 13:46 +0200, Hendrik Helwich wrote:
> Am 20.10.2010 10:55, schrieb Georg C. F. Greve:
> > [..]
> > What I would like to see more input in would be the "floating" time zone
> > concept that translates "to wherever you are right now" as explained by
> > Bernhard in his mail to this thread.
> >    
> Hi Georg,
> i am not sure if i understood this concept. Bernhard described it like this:
> > There is a third case that I darkly remember: Floating local timezone.
> > (Currently we do not support it.) Example: Do your excercises at eight in the
> > morning, no matter where you are.
> I think this would even be more complicated. The event must be related 
> to a specific user and must track its timezone.
> Or does this event should happen always at the same local time for 
> everybody no matter in which time zone this person is?

This is what floating time is intended to be.  It is something like
'daily at 8:00am in the local timezone of the user currently viewing the
event'.  There is no timezone.  There is no daylight saving change.
There is no offset from UTC.  Just the date & time, plain and vanilla.

It actually works fine for meetings where all participants will always
be in the same timezone and some software actually uses this as it's
default method for constructing events.  For example I believe that
Apple iCal creates all events in a floating time unless you have turned
on timezone handling.

Floating time is not intended to cover the use case of a secretary
briefing their boss at 8:00am in their boss' timezone.  While this is an
interesting concept I don't believe there are actually many people who
would even want to try and schedule such a thing, especially given the
requirement for automatically updating location and timezone for a

Maybe in ten years something like this might emerge as an occasional
real-world requirement where there is more ubiquitous updating of actual
location.  I would call this situation something more like 'time
localised to a specific person's varying timezone' rather than 'floating
time', which is intended to be the simplest way of recording time.

When I have worked with people who are constantly travelling, and who
have assistants to provide them with such briefings, the assistants have
been more likely to know their boss' intended timezone before their boss
did, and the briefings are likely to be by way of an e-mail summary,
prepared during working hours back at the home office in most cases.

> If it is like this it would not be useful for an event which is shared, 
> because then everybody would come to a different time to that meeting if 
> the people are in different time zones.

Well, there are circumstances where it would be incredibly useless, but
in fact it works fine for most situations, and it does have the benefit
of bypassing any need for calculating daylight savings offsets or such.

Most people are fortunate not to have to deal with so many cross-
timezone meetings as I do (I live in New Zealand and my clients mostly
don't, so my meetings are frequently cross-timezone phone/video/chat
arrangements, with a time difference of 2, 3, 12, 13, 15, 16, 17, 18,
19, 20 or 21 hours depending on whether one, or both of us are in DST)
but people normally just go to the office and meet with people who are
also in the same city, and it turns out that floating time works just as
well for that, as it does for taking my medication every morning when
I'm travelling.

					Andrew McMillan.
andrew (AT) morphoss (DOT) com                            +64(272)DEBIAN
We can embody the truth, but we cannot know it.
                -- Yates

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