Date Countries Switch to/from DST

[O'Neil, Bonnie]

Guy,
You are right.
As we understand it, countries may make an announcement that they will
be observing DST this year on such and such a date.  What we need is to
keep track of these pronouncements as they relate to our flight
schedules.
We will have to map countries & cities to the locations. I will check
out the resources you site here.
This list has been very helpful!


Bonnie K. O'Neil
CBIP, CDMP
Enterprise Data Architect
Travelport Global Technology Solutions
Office: 303-397-5239
Mobile: 303-725-1737


-----Original Message-----
From: Guy Harris [mailto:guy at alum.mit.edu] 
Sent: Friday, February 04, 2011 4:12 PM
To: tz at lecserver.nci.nih.gov
Subject: Re: Date Countries Switch to/from DST


On Feb 4, 2011, at 9:15 AM, O'Neil, Bonnie wrote:

> I need to get a dump of the tz database for all countries in the
world, which timezone they are in, and what date they switch on/off DST.

Note that "the tz database", in the sense of the database available for
FTP from elsie.nci.nih.gov (which is where the tz-link.htm page points),
and which this list discusses, doesn't directly have "countries"; the
name of a "time zone" in the database corresponds to a "location" - to
quote the tz-link.htm page:

	Each location in the database represents a national region where
all clocks keeping local time have agreed since 1970. Locations are
identified by continent or ocean and then by the name of the location,
which is typically the largest city within the region. For example,
America/New_York represents most of the US eastern time zone;
America/Phoenix represents most of Arizona, which uses mountain time
without daylight saving time (DST); America/Detroit represents most of
Michigan, which uses eastern time but with different DST rules in 1975;
and other entries represent smaller regions like Starke County, Indiana,
which switched from central to eastern time in 1991 and switched back in
2006.

I infer from your company's name and Web site that one thing you
probably need is a way to map a geographical location to a tz database
location (for example, "what timezone is Paris in and when do they
switch on/off DST?").  The tz database doesn't itself provide that, but
at

	http://efele.net/maps/tz/world/

you can get a file that shows the boundaries of tz database locations;
at

	http://www.manifold.net/info/freestuff.shtml

are a bunch of data sets, include a map of "World Time Zones", although
they don't say whether that's a map of tz database locations or not.

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