Internationalization: Support for IANA time zones

Mark Davis ☕ mark at macchiato.com
Sat Mar 2 08:46:54 PST 2013


On Sat, Mar 2, 2013 at 5:11 PM, Shawn Steele <Shawn.Steele at microsoft.com>wrote:

> I’m uncomfortable using the CLDR names, although perhaps they could be
> aliases, because other standards use the tzdb names and we have to be able
> to look up the tzdb names.  It might be nice to get more stability for the
> tzdb names, like aliases or something.****
>
>
​I'm simply not explaining myself correctly. *The CLDR IDs (long IDs) *ARE*
tzdb IDs.* Let me give you a specific case.

The TZDB has the equivalence class {Asia/Calcutta Asia/Kolkata}. They used
to have the former as the canonical name (in Zone), but then changed it to
the latter. Here is the current TZDB data:

zone.tab

IN +2232+08822 Asia/Kolkata


asia

Zone Asia/Kolkata 5:53:28 - LMT 1880 # Kolkata
...


backward

Link Asia/Kolkata Asia/Calcutta


Because of the Link, both are valid and equivalent.


CLDR, because we need stability, retains the *former* TZID as the canonical
name. That is the meaning of the first alias in
http://unicode.org/repos/cldr/tags/release-22-1/common/bcp47/timezone.xml such
as in:

<type name="inccu" alias="*Asia/Calcutta* Asia/Kolkata" description="Kolkata,
India"/>

The short name (name="...") is only used for BCP47 subtags (because of the
ASCII/8-char limit), *not* for communicating with TZDB implementations. Nor
is it used in CLDR for the canonical ID.

Instead Asia/Calcutta is used as the canonical ID. Here are some of the
samples of the localizations.

<zone type="Asia/Calcutta">
<exemplarCity>ኮልካታ</exemplarCity>
</zone>
...
<zone type="Asia/Calcutta">
<exemplarCity>Kolkata</exemplarCity>
</zone>
...
<zone type="Asia/Calcutta">
<exemplarCity>コルカタ</exemplarCity>
</zone>

and so on. Note that these are all TZIDs.

The only long ID that CLDR adds is one to indicate an unknown/illegal TZID:

<zone type="Etc/Unknown">
<exemplarCity>地域不明</exemplarCity>
</zone>


Is the picture clearer now?


Mark <https://plus.google.com/114199149796022210033>
*
*
*— Il meglio è l’inimico del bene —*
**
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