Time Zone Localizations
eggert at CS.UCLA.EDU
Mon Jun 14 04:16:36 UTC 2004
"Mark Davis" <mark.davis at jtcsv.com> writes:
> 1. What are the all valid Olson TZIDs
> 2. How to determine which are 'canonical' and which are simply included for
> 5. An explicit description of the data representation for all of the
> data files.
We've covered these issues in our emails so far, I think, so all you'd
need to do is write it all down.
> 3. What is the meaning of an TZID
Sorry, I don't know what you mean by "meaning of a TZID".
A TZID is just a name. But perhaps you can just consult
the Theory file to see the naming convention.
> 4. What is the versioning scheme,
You can get many (most?) old versions at
<ftp://munnari.oz.au/pub/oldtz/>; the versioning scheme should
be fairly evident though I suppose it wouldn't hurt to write it up.
> including assurance that:
I'm afraid there is no warranty of any kind. This is entirely an
informal volunteer effort.
> - once a version is issued it is never changed.
That's been true in practice. For example, once tzdata2003d.tar.gz
was issued, it wasn't changed; instead a newer version
tzdata2003e.tar.gz was issued.
> - TZIDs are stable, in the sense that they will never be withdrawn or reused
> with a substantially different semantic in later versions
That's also been true in practice, mostly. Generally speaking, TZIDs
are never withdrawn; they're just moved to the 'backward' file.
However, I can think of one exception. In 1994 some of the
GMT-related TZIDs did change their semantics to conform to POSIX. For
example, the old TZID "GMT-12" was withdrawn and its replacement is
called "Etc/GMT+12"; this because POSIX required a different semantics
for TZ="GMT-12". This sort of confusion is one of the reasons why I
don't encourage the use of TZIDs like "Etc/GMT+12".
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