[tz] time zone abbreviations - uniqueness and meaning

Tobias Conradi tobias.conradi at gmail.com
Thu May 24 10:11:32 UTC 2012

was: Re: [tz] Propose new zone for Crozet Islands

On Thu, May 24, 2012 at 10:40 AM, Philip Newton <philip.newton at gmail.com> wrote:
> On Thu, May 24, 2012 at 9:46 AM, Tobias Conradi
> <tobias.conradi at gmail.com> wrote:
>> The rule in the Theory file can easier lead to double assignments of
>> abbreviations
> I don't think a particular effort is made to make the abbreviations be
> unique
I don't know how you define "particular".

The provision to use ISO 3166-1 alpha-2 codes for several of them
leads to several of them being unique.

IIRC there have been emails on the mailing list caring about
uniqueness, asking for assignment of another abbreviation to avoid

contains a longer text by Paul Eggert 2001-04-05 about uniqueness.

> or even particularly meaningful.
I don't know how you define "particularly".

----- Outline -----
	Time and date functions
	Scope of the tz database
	Names of time zone rule files
	Time zone abbreviations
	Calendrical issues
	Time and time zones on Mars
one of six main sections.

The section "Time zone abbreviations" contains several rules. They all
derive the abbreviation from some other string related to the time

> The main identifier is the
> "Europe/Berlin" type name,
that is the IANA time zone name. IANA time zones are "cross year".

> not the "CE(S)T" type one.
that is the IANA abbreviation for the non-IANA, the "real world" time zone.

One can try to achieve uniqueness of the latter in any given year.

The two uniquenesses can be achieved independently.

But indeed there are some that are not unique, e.g.:
** India
** Israel (Ephraim Silverberg 1988 invention, even happy about
ambiguity: "I am happy to share timezone abbreviations with India,
high on my favorite-country list (and not only because my wife's
family is from India" ftp://ftp.iana.org/tz/data/asia )

** Australia
** US

** Australia
** US

** Arabia (Eggert invention 2006-03-22 ftp://ftp.iana.org/tz/data/asia)
** Aruba, Curacao, Trinidad and Tobago

** Gulf (Eggert invention 2006-03-22 ftp://ftp.iana.org/tz/data/asia)
** South Georgia and the South Sandwich Islands

ICT	Indochina (Eggert invention 2006-03-22 ftp://ftp.iana.org/tz/data/asia)

IC is a reserved ISO 3166-1 alpha-2 element for the Canary Islands.

Tobias Conradi
Rheinsberger Str. 18
10115 Berlin


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