[tz] Converting from individual cities/states/country names to Windows time zone names

Daniel White twinbee42 at skytopia.com
Tue Dec 6 14:08:46 UTC 2011

 <yoshito_umaoka <at> us.ibm.com> writes:

> > What I have been able to find is a way to convert
> from TZID (Olsen) 
> > to Windows 
> > timezone IDs using this URL:
> > http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/zone_tzid.html
> I'm planning to update the data to support multiple
> TZID mapping (One Windows TZ -> Multiple TZIDs) in CLDR. I was considering
> this before, but it's quite a tough task (also keeping data up-to-date
> is not trivial).
> It looks you're trying to create mapping data from
> location to Windows time zone. You would find how difficult to achieve
> this soon.
> There are several type of issues.
> 1) No matching UTC offset in Windows
> For example, Australia/Eucla uses UTC+08:45 as base
> offset, but there is no such zones in Windows time zone list. There are
> several other instances.
> 2) No matching daylight saving time rule in Windows
> For example, Pacific/Easter observes daylight saving
> time from August, 2011 to March 2012. However, Windows does not have any
> UTC-06:00 zones supporting the daylight saving time rules (Windows UTC-06:00
> zones are all Northern Hemisphere type rules).
> 3) Ambiguous mapping
> For example, Windows has following time zones with
> UTC+09:00 / no DST.
> (UTC+09:00) Osaka, Sapporo, Tokyo
> (UTC+09:00) Irkutsk
> (UTC+09:00) Seoul
> You have to decide one from above for some other territories
> using UTC+09:00/no DST. For example, Asia/Dili, Asia/Jayapura, Pacific/Palau.
> 4) Out of date data
> You may want to map Belarus to (UTC+02:00) Minsk.
> However, Minsk (Belarus) is currently using UTC+03:00/no DST.
> Microsoft suggests Windows users in Belarus to use
> (UTC+03:00) Kakiningrad for now [http://support.microsoft.com/kb/2625508].
> -Yoshito


Thanks for the info. What you said makes me wonder even more Why Microsoft
didn't go with TZID, and instead create their own half-baked substitute. A
fine example of why standards are so important, and how the TZID system is
of such great benefit to the world.

In the end, I understand the flaws of Windows' time zone system, but I think
I'll have to make do, as an alternative (for C#) would be many times the size
of my own program. And I'm too keen on the user accessing the internet each

Cheers, Dan

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