Date Countries Switch to/from DST

Guy Harris guy at
Fri Feb 4 23:12:00 UTC 2011

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 (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

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

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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