[tz] efele.net/tz maps updated

[L. David Baron]

On Sunday 2015-11-29 09:31 -0800, Eric Muller wrote:
> I started the maps while TZ still had a policy that a timezone would be
> "contained" in a political entity. When the great zone unification happened,
> I was faced with the choice to apply or not that unification to the maps. As
> it was a bit unclear where TZ would end up, and because it's easier to merge
> the shapes for those zones (it only takes data in TZ) than to split them
> (had I done the unification), I elected to retain as many zones as possible
> (see my message to this list on July 26, 2014). I took all the zone names
> that existed, rejected names like Etc/GMT+10, rejected names that are
> obviously aliases for the same geographical extent (eg Africa/Asmera,
> retaining Africa/Asmara), and kept all the others.
> 
> It should be a trivial matter to take any equivalence relation on the zones
> and produce a map that has a single shape for each class. The equivalence
> relation could be "zones are linked", or "zones have the same local time
> over a given period of time".

This sounds reasonable.

It's not clear to me whether this is still accurate for China,
though.  It seems that the map data in
http://efele.net/maps/tz/china/ are based on what is now described
(I think) in the asia file in the tz source as being pre-1949 zones.
These boundaries include areas in Asia/Urumqi (most suspiciously a
few counties in Guangdong, and also parts of Qinghai and Gansu) that
it's not clear to me are intended to be in Asia/Urumqi following the
recent changes in 
https://github.com/eggert/tz/commit/15b01c042afa770acd5068054c50e7c5c663cbd2
which unify China's 5 zones into 2, and put Asia/Urumqi in UTC+6
rather than UTC+8 (along with Asia/Kashgar, which is now a link to
Asia/Urumqi).  When combined with the regions in your map data, this
implies that Western Guangdong province (the counties of Xuwen,
Haikang, Suixi, Lianjiang, Zhanjiang, Wuchuan, Huazhou, Gaozhou,
Maoming, Dianbai, and Xinyi) is on UTC+6 today, and the same for
western parts of Qinghai and Gansu (which seems more reasonable, but
which I didn't see mentioned in the comments introduced in that
commit).

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
             Before I built a wall I'd ask to know
             What I was walling in or walling out,
             And to whom I was like to give offense.
               - Robert Frost, Mending Wall (1914)
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