Geographical boundaries for the continental US tz zones

Paul Eggert eggert at CS.UCLA.EDU
Thu May 31 20:32:58 UTC 2007

Eric Muller <emuller at> writes:

> 1. I would think that America/Boise, America/Denver and
> America/Phoenix together correspond exactly to the Mountain time zone
> of timeznp020. However, the later includes the southern quarter of
> Idaho County, Idaho, while northamerica suggests that this county is
> entirely in America/Pacific. Who is right?

Most likely the National Atlas, if nobody says differently.  You can
consult the U.S. Department of Transportation (DOT) to make sure.
Might have to call them or consult printed records...

> 2. The description of America/Denver includes "far eastern Oregon",
> and the description of America/Boise includes "eastern
> Oregon". Comparing with timeznp020, I suspect that America/Denver
> should not include "far eastern Oregon". (and if timeznp020 is right,
> "eastern Oregon" could be better described as "most of Malheur County,
> Oregon").

Sounds good.

> 3. What does America/Indiana/Indianapolis cover? Is it all the
> counties of Indiana not listed in any of the other zones?


> However, it seems that Pulaski now has it own zone
> (America/Indiana/Winamac), so it should probably be moved from the
> first to the second bullet in the quote above.

Yes, thanks.

> 5. The description of America/Indiana/Marengo is that it covers the
> eastern part of Crawford County. How is that county divided, and in
> which zone does the western part fall?

> 6. What part of Kentucky goes in America/Kentucky/Louisville?

For both questions, I haven't a clue, but you may be able to tell by
looking at old DOT records.

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