I'm trying to present the (web) user with a useful subset of Olson timezones, though with a friendlier naming convention.
Any recommendations for how to sort and label them for maximum usefulness? By country? Continent? GMT offset?
I'm not very concerned about inaccuracy for past dates, so some of the timezones that are only historically different could be winnowed out, but I'm not sure it's worth the effort of identifying which. If someone else already has done so, please let me know.
I've not done it myself, but personally I would simply sort by GMT offset. I think everyone knows what timezone they're in generally so that gives the easiest/quickest way to find what people are after.
I've always thought the Windows way was good - a map of the world where you click on your location.
However, if you want a dropdown, you need to think "what will most people know about their location?".
To me, that would be the country or state or region they're in. So I would provide a number of dropdowns which gradually reduced the resolution (country, state, town for example) and at the end a timezone would pop out.
Sorting by GMT offset is usual, optionally followed by the name of a major city in that zone. Remember that time zones can be on 30 & 15 minute boundaries, not just hours! They can also be greater than 12 hours from GMT, due to daylight savings.
(Edited to add more information)
I'd try a GMT-offset approach - some countries have more then just 1 timezone (US for instance). Although users usually know what timezone they're in, some might not.
Why not try giving a GMT offset together with current time in that timezone? Then even if someone does not know what's his/her offset, he/she will instantly see it just by checking own clock.
Edit: ask yourself who your target audience is. Is it a geek who uses stackoverflow.com and knows what to expect from a timezone-selection dropdown? Or a housewife, who just wants to check a reciepe on your site and go back to cooking, and all she really cares about timezones is to not call her sister who lives on the other side of the world.
Don't forget New Zealand which is normally GMT+12, but goes to GMT+13 in the summer!
Definitely GMT offsets. Browsing by alphabetical order is hard if you don't know what you are looking for. I live in Sweden, should I look for Sweden or Stockholm? Or perhaps Paris?
Really big drop downs are a pain to for the user. To make the list shorter you should group equivalent timezones (like "GMT+1 Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna").
The answer depends on the sophistication of the timezone support.
Minimal - "one selection per hour.'
Looking at the original iPod, the timezone selection is simply a list of zones. Each appears twice, with a non-DST and a DST entry.
iPod (root menu) -> Settings -> Date & Time -> Set Time Zone -> (list).
Example entries:
There appear to be about ~20 pairs, so this is probably a list of "heavily populated zones". Since the built-in clock does not support auto-DST calculations, this is really a "I got off the plane and I want to hack my clock temporarily" interface.
A sizable number of rarer use cases are not supported, like non-hour offsets.
Fully featured - time zone selection
If the number if time zones is small, I would present the "Area/Location" format, sorted by standard GMT offset.
Sorting by the current offset (Standard vs. DST) is probably too much work, and the general order will be the same. Most people understand time zones enough where they can pick the correct on.
The most important factor is number of items. If the list gets very long, then you might want to used a multi-tab list, where you make a geographic grouping (or simply make the tabs group by "Area").
I am working on the time zone support of several products right now, and that is my recent experience.
I struggled with this for a while, and I put this is as the first post in my new blog http://www.aviblock.com/blog/2009/03/12/presenting-a-list-of-timezones-to-the-user/ My basic approach was to first trim the list and remove duplicates (duplicates being any timezone that has the same transition dates for DST (if applicable) for 2009 and the same GMT offset for those dates, is considered a duplicate. This brought me down to about 80 from ~560. After that, I just had to come up with good names for those timezones. I chose something similar to (and borrowed from) the windows format (GMT-07:00 Arizona is the timezone in the united states which is mountain time but doesn't observe DST, represented by Olson tzid America/Phoenix)