Evolution should have user interface for traveling to a different timezone *for
a specific period of time*.  Currently it has a global timezone setting. 
However, this isn't very useful when traveling.  If I'm going to be nine
timezones away for a week, I want to see my events for that week in the timezone
where I'll be in that week; when they're put in the correct timezone they often
don't even show up on the correct day, since the day is different between the
time zones.

For example, I was in Australia from January 28 through February 4 (19 hours
time difference from California).  I want to see the appointments *for the
period when I'm in Australia* in Australia time, no matter what timezone I'm
currently in.  Likewise, for the week I'm in Australia (since I currently change
my global timezone setting when I travel), I want to see the appointments for
when I get back in California time; I don't want my Tuesday meetings showing up
on Wednesday while I'm in Australia.

There are two possible approaches to providing user interface for this that I,
and others that I've discussed this issue with, have thought of:

 1. Provide some out-of-band user interface for specifying a different time zone
for a given time range.

 2. Deduce time zone changes from events that start and end in different
timezones.  You wouldn't necessarily have to do this by default for all events;
there could be a per-event checkbox or a global preference.  However, I think
events that start and end in different timezones are rather rare, and tend to
represent travel.

I strongly prefer solution #2.

If solution #2 is taken, there *may* be some value to warning about unbalanced
travel events, i.e., a situation where the last travel event ends in a
non-default timezone.