[tz] tz dependency lat & lng

Guy Harris guy at alum.mit.edu
Thu Sep 5 21:16:28 UTC 2013

On Sep 5, 2013, at 1:54 PM, Lester Caine <lester at lsces.co.uk> wrote:

> The reason that an adminastrative boundary for timezone is not yet available is because nobody has had time to create it. It will use elements of existing relations, but to be honest the current thinking is that simply tagging elements that have a unique timezone with that information. That way when one looks up a place record you get the information without having to do a geometric search.

If all you have is longitude and latitude, you're going to have to do a geometric search.  There might not *be* a place record for where you are, and, even if there is, it won't necessarily have a tag.  They claim to have 105 places tagged with America/New_York; to quote


"New York has 62 counties, which are subdivided into 932 towns and 62 cities;[4] it also has 10 Indian reservations.", so that's about 10.5% of New York State, and America/New_York also includes:

	New Hampshire
	New Jersey
	North Carolina
	Rhode Island
	South Carolina
	West Virginia

and parts of some other states as well.  They probably have the major cities covered, but

	1) there are probably plenty of UN*X boxes using the tzdb outside of those major cities


	2) the vast majority of smartphones sold in the US are probably UN*X boxes using the tzdb (I'm guessing Bionic uses the tzdb; Darwin's libSystem definitely does), and they can be on the road *between* places.

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