[Talk-us] Timezones in USA?

[evan.siroky at yahoo.com]

Are there any people / groups / organizations working on adding the "timezone" tag to various boundaries in the USA?
I did some research on this subject and found the following:

The timezone boundaries in the USA are established by the US DOT.  They publish a document specifying the exact boundaries of each timezone here:  https://www.gpo.gov/fdsys/pkg/CFR-2011-title49-vol1/xml/CFR-2011-title49-vol1-part71.xml

I found and read through this OSM mailing-list discussion about timezones from a few years ago: https://lists.openstreetmap.org/pipermail/talk/2013-October/068334.html  It seems there are mixed feelings for how to include timezone data in OSM.
As for timezone tags being in OSM, there are plenty of items that have a timezone tag according to taginfo:  http://taginfo.openstreetmap.org/keys/?key=timezone
I downloaded Mapzen's OSM border data extract for the USA and analyzed the data in QGIS.  I found that 35 states or territories and 200 counties have a timezone tag.  I also found that zero cities or townships had a timezone tag.
The data isn't completely correct in some edge cases and also the dividing line between America/Denver and America/Chicago is non-existent (at least at the state/county level).  However, in certain places the data is very good, for example all of the counties in Florida and Tennessee are tagged correctly based on whether they are in the America/Chicago or America/New_York timezone.  
It seems the current methodology for adding timezone data is adding a tag at the highest level of administrative boundary that is completely encapsulated within a timezone.  For example, a state that contains multiple timezones would not have a timezone tag, but instead all of the state's counties would.  However, there are still a few small quirks that would not be covered by this methodology: 1) cities that use a different timezone and 2) timezone boundaries that don't share a boundary with any other administrative boundary.
In the example of a city having a different timezone is West Wendover, NV which is on the border of Utah.  The city is in the timezone America/Denver, whereas the state of Nevada is otherwise completely within America/Los_Angeles.  Perhaps it would be possible in this case to add a timezone tag to the city boundary while still keeping a timezone tag at the state level which could be interpreted as an exception to the state-level data.
The other example is trickier: the upper 3/4ths(ish) of Malheur County in Oregon is in the America/Boise timezone whereas the lower 1/4th(ish) is in America/Los_Angeles.  Perhaps the only way to model this in OSM would be to create two new relations comprising of the borders of the county and then a new way that is only a boundary for the timezone in that county.
I'm asking all of this because I'm interested in improving the data quality of timezone boundary data.  I am aware of the shapefile of timezones at http://efele.net/maps/tz/world/, but it doesn't include territorial waters and the underlying data doesn't appear to be open/editable.  It seems like OSM could be a place to store at least part if not most of the timezone boundary data.
Would anyone object to adding the timezone tags to the rest of the states/counties that are completely encapsulated by a timezone?  What about the city example?  What about adding a way that is only useful for dividing a timezone within a county?  I look forward to the discussion.

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