Implementation of zoneinfo (Olson, tz) database in .NET c-sharp csharp

yoshito_umaoka at yoshito_umaoka at
Fri Jun 22 15:21:41 UTC 2007

Masayoshi.Okutsu at Sun.COM wrote on 06/22/2007 07:31:53 AM:

> On 6/22/2007 4:31 AM, Paul Eggert wrote:
> > Does this mean that the Windows-Tzid table maintained by the
> > CLDR project is incorrect, or that CLDR needs a new table for Vista?
> > If so, we should warn the CLDR folks about the problem.  Please see
> > <>.
> > 
> Some time ago I pointed out that there's no concept of tzid on Windows, 
> and I asked how CLDR got these "Windows-Tzids." But I don't think I got 
> any answer.

These is no concept of tzid on Windows, but at least MS maintains
registry keys under -

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones

My understanding is that CLDR folks assumed these "time-zone strings" as

MS defines a sort of tzids called "CodTimeZoneId" for Exchange/Outlook.

These are obviously a subset of Windows "Time Zones" registries.

> The Java runtime uses the GetTimeZoneInformation() and "Time Zones" 
> registry values to detect the current Windows time zone and map it to a 
> tz database ID using some complicated method. You may want to check 
> <JRE_HOME>\lib\tzmappings in JRE/JDK 6 for Windows and the runtime code 
> for detecting the current Windows time zone. The source code can be 
> downloaded from
> Masayoshi

Windows used to support only a pair of DST start/end rules per zone,
but MS finlally implemented a framework for supporting historic
changes since Windows Vista.

I do not think this enhancement has any impacts to Java runtime on
Windows although.


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