Chamorro Standard Time (new US time zone)

Paul Eggert eggert at
Wed Jan 10 17:06:56 UTC 2001

> From: "INFOMAN Inc." <mpereira at>
> Date: Tue, 9 Jan 2001 10:29:04 -0500

> Are there any rules for the use of uppercase/lower case Latin-1
> characters for labels for time zones? You state that POSIX allows
> for this.

POSIX.1-1996 says that an abbreviation cannot start with ':', and
cannot contain ',', '-', '+', NUL, or a digit.  Draft 5 (d5) of the
next POSIX changes this rule to say that an abbreviation can contain
only '-', '+', and alphanumeric characters in the current locale.  To
be portable to both sets of rules, an abbreviation must therefore use
only ASCII letters, as these are the only letters that are alphabetic
in all locales.

The current Theory file says that only upper-case ASCII letters should
be used, because that "follows most traditions".  These traditions
date back to when upper-case-only terminals were common.  However,
nowadays this is less of an issue, and it seems reasonable to relax
this rule to allow lower-case characters.  (Besides, who am I to
second-guess a Congressman? :-)

The current Theory file also suggests that "___" be used as the
abbreviation when a location is uninhabited.  Currently this
convention is used only for Antarctic stations.  "___" can be
generated by a POSIX.1-1996 TZ string, but not by a d5 TZ string.
I guess we should change "___" to some other abbreviation.
"zzz" comes to mind, as uninhabited locations are, in some sense, asleep.

> However, I would suggest that, we continue to use upper case only.
> Otherwise what is to prevent one source from using "ChST" and
> another source using "CHST"?

Nothing.  But we already have the problem of different sources using
different abbreviations.  For example, for eastern time in Australia,
some sources use EST, some AEST, and some EAST.  The best we can do is
pick the most commonly-used abbreviation.  In the case of Chamorro
Standard Time, we currently have only one reported use, which was in
the December 27 press release of the Congressman who drafted the law.
If common use turns out to be different, we can change it later.

> Further by allowing lower case, one makes it easier to introduce the
> use of diacritics (e.g.  é,ö,ñ, etc.

That wouldn't be portable, as discussed above.

> 1. Is there an "official list" of all the names or labels used to
> designated time zones

No, unfortunately.  And in practice, the names are ambiguous.  For
example, "IST" means UTC+2 in Israel, but UTC+5:30 in India.
Simiarly, "EST" has different meanings in the US and in Australia.
Even if you limit yourself to Australia, "EST" can mean UTC+10 or
UTC+11, depending on the time of year.

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