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

Ephraim Silverberg ephraim at
Thu Jan 11 07:40:45 UTC 2001

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

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