lat/lon to time offset database

[Guy Harris]

On Feb 3, 2011, at 10:54 AM, Paul Koning wrote:

> The zone.tab file might seem like a starting point, but it isn't really; it just lists each of the zones with a single point in that zone.  What you need is the analog of zone.tab but with the bounding polygon for each zone rather than a point inside it.  I believe that data exists somewhere, but I don't remember the location.

The tz-link.htm file I mentioned in my previous message has a section "Time zone boundaries" that says:

	• TZ timezone maps contains a shapefile of the tz regions in the world.
	• Administrative Divisions of Countries ("Statoids") contains detailed lists of tz-related zone subdivision data.
	• Time zone boundaries for multizone countries summarizes legal boundaries between time zones within countries.
	• Manifold.net's Free Maps and GIS Data includes a Manifold-format map of world time zone boundaries distributed under the GPL.
	• The US Geological Survey's National Atlas of the United States publishes the Time Zones of the United States in the public domain.
	• The GeoCommunity lists several commercial sources for International Time Zones and Time Zone Data.
	• A ship within the territorial waters of any nation uses that nation's time. In international waters, time zone boundaries are meridians 15° apart, except that UTC−12 and UTC+12 are each 7.5° wide and are separated by the 180° meridian (not by the International Date Line, which is for land and territorial waters only). A captain can change ship's clocks any time after entering a new time zone; midnight changes are common.

The links for those are:

	http://efele.net/maps/tz/ - the "TZ timezone maps" link (mentioned in another message); "shapefile" links to http://en.wikipedia.org/wiki/Shapefile, which describes what a shapefile is

	http://statoids.com/statoids.html - "Administrative Divisions of Countries ("Statoids")

	http://home.tiscali.nl/~t876506/Multizones.html - "Time zone boundaries for multizone countries"

	http://www.manifold.net/download/freemaps.html - "Manifold.net's Free Maps and GIS Data", but that link no longer works

	http://nationalatlas.gov/mld/timeznp.html - "Time Zones of the United States"

	http://spatialnews.geocomm.com/features/timezones/ - "The GeoCommunity lists several commercial sources for International Time Zones and Time Zone Data."