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Re: canonical names for timezones

From: John Cowan <jcowan@reutershealth.com>
Date: Thu, 23 Aug 2001 14:49:39 -0400
Message-ID: <3B855043.2010202@reutershealth.com>
To: Lenny Turetsky <LTuretsky@salesforce.com>
CC: "W3intl (E-mail)" <www-international@w3.org>
Lenny Turetsky wrote:

> But how do we communicate their timezone? Is GMT offset sufficient? GMT
> offset + daylight savings time (on/off)?

Definitely not.  I recommend that you use the time zone names from
the "tz" package by Arthur David Olsen, which provides both data and C
code (Java also available).

Timezone names in this package are usually
of the form Continent/MajorCity or Ocean/MajorCity, since cities
are rarely renamed (much less often than countries).  Zones do
not cross national boundaries (since national legislatures often
change the rules), and any two places that have had different rules
at least once since 1970 are in different zones.  There are about 400
altogether.

For example, the four main U.S. zones are called America/New_York,
America/Chicago, America/Denver, and America/Los_Angeles, but
the following zones are also used in the U.S.:

	America/Juneau (all in Alaska)
	America/Yakutat
	America/Anchorage
	America/Nome
	Pacific/Honolulu (Hawaii)
	America/Phoenix (Arizona, no DST)
	America/Boise (Idaho, different DST rules in some years)
	America/Indianapolis (Central with DST some years, EST others)
	America/Indiana/Marengo (different Indiana counties)
	America/Indiana/Starke
	America/Indiana/Vevay
	America/Louisville (no DST in Kentucky some years)
	Indiana/Kentucky/Monticello
	America/Detroit (no DST in Michigan)
	America/Menominee (Central with DST some years, EST others)
	
But luckily for you, if you use the existing tables and code you have
no need to manage all this complexity.	
		
For details:  http://www.twinsun.com/tz/tz-link.htm has links to
the tz database and open-source code, and many other good things.
There is a mailing list at tz@elsie.nci.nih.gov full of very
helpful people.

-- 
Not to perambulate             || John Cowan <jcowan@reutershealth.com>
    the corridors               || http://www.reutershealth.com
during the hours of repose     || http://www.ccil.org/~cowan
    in the boots of ascension.  \\ Sign in Austrian ski-resort hotel
Received on Thursday, 23 August 2001 14:50:32 GMT

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