IST/IDT [Re: Chamorro Standard Time (new US time zone)]

Syed Sajjath Syed.Sajjath at
Thu Jan 11 17:07:31 UTC 2001


I work on an application which uses international timezone abbreviations.
It makes sense to use the most popular abbr. used within the country, since,
clients within the country understand that.  I believe tzdata is the best
source for this purpose, as people all over the world contribute to it.

In our application we always use the abbr., in conjunction with the country,
avoiding ambiguities.  More examples are CST, EST and PST used both in
Australia and US.


-----Original Message-----
From:	ephraim at [mailto:ephraim at]
Sent:	Thursday, January 11, 2001 1:41 AM
To:	Paul Eggert
Cc:	tz at
Subject:	IST/IDT [Re: Chamorro Standard Time (new US time zone)]

On 10 Jan 2001, Paul Eggert wrote:

>> 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.

I have to take responsibility for that ambiguity as I coined "IST/IDT"
circa 1988.  Until then there were three different abbreviations in use:

JST  Jerusalem Standard Time [Danny Braniss, Hebrew University]
IZT  Israel Zonal (sic) Time [Prof. Haim Papo, Technion]
EEST Eastern Europe Standard Time [used by almost everyone else]

Since timezones should be called by country and not capital cities,
I ruled out JST.  As Israel is in Asia Minor and not Eastern Europe,
EEST was equally unacceptable.  Since "zonal" was not compatible with
any other timezone abbreviation, I felt that 'IST' was the way to go
and, indeed, it has received almost universal acceptance in timezone
settings in Israeli computers.

In any case, 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).
Ephraim Silverberg, CSE System Group,        Phone number:    972-2-6585521
Hebrew University, Jerusalem, Israel.        Fax number:      972-2-6585439
WWW:       E-mail: ephraim at

More information about the tz mailing list