[tz] tzid in zoneinfo?

Arthur David Olson arthurdavidolson at gmail.com
Thu Feb 9 22:59:23 UTC 2017

The tzid might be stored as a seemingly extraneous time zone abbreviation,
presumably with magic characters ("TZID"?) prepended or appended for
identification purposes. Other such information could be included using the
same approach.

The fifteen "reserved for future use" bytes near the start of time zone
binary files are too few for this purpose (take "America/New_York"--and cue
Henny Youngman).


On Thu, Feb 9, 2017 at 5:44 PM, Steven R. Loomis <srl at icu-project.org>

> Dear TZ list,
>  I would like to propose that zic-compiled binaries (such as what shows
> up in /etc/zoneinfo) include the tzid (such as ‘America/New_York’).
>  I work on the ICU project (Unicode’s International Components for
> Unicode) and also CLDR (Unicode’s Common Locale Data Repository).  The
> ICU library consumes tz data, and uses the localized data from CLDR to
> (among other things) display translated time zone names of various
> sorts, and format different types of dates.
>  A perpetual problem is trying to detect the actual timezone of a
> platform. Ideally something like the TZ variable is set to a valid tz id
> such as America/New_York which we can use directly.  Otherwise, we try
> various approaches - including trying to resolve /etc/localtime’s
> symlink to see if it points to a file which appears to be in some sort
> of zic-compiled tree. This brings up bugs such as
> http://bugs.icu-project.org/trac/ticket/12770 because various platforms
> use different paths as the targets of /etc/localtime - and some times,
> it's a doubly linked symlink.  In other cases, the file is just copied,
> and we have to trawl through /usr/share/zoneinfo looking for a binary
> file which matches.  There are other methods employed if these fail, but
> I think this will suffice for our purposes.
>  Even if ICU consumed the /etc/zoneinfo file directly, or was able to
> call the host to perform the calculations it needs, that would not
> suffice in terms of localized content.  As I think has been noted on
> this list before, it does not seem to be a goal of the tz database to
> collect these translated names, and tz-link.html does link to CLDR as
> one possible source of translations.
>  I think that this would benefit other users as well, by making zone
> files self identifiable. I think the JDK has to do similar analysis.
> Some JavaScript containers (Mozilla especially) now support IANA tz ids,
> such as in
> https://developer.mozilla.org/en-US/docs/Web/JavaScript/
> Reference/Global_Objects/DateTimeFormat#Parameters
>  Any thoughts or comments?
>  Thanks,
>    Steven
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