Pac/Mtn border at Winterhaven California)

Steve Jones stevejones at
Mon Sep 12 19:03:04 UTC 2011

At 06:54 9/12/2011, Alois Treindl wrote:
>I have researched in newspaper archives, and found an article in the 
>paper 'The Mountain Democrat Times' of 1968 March 28, which confirms 
>that the whole area on the Yuma AZ side of the Colorado River but 
>belonging to California followed even then Arizona time, i.e. MST 
>without observing DST.
>It mentions the post office in Bard, CA as an example, and probably 
>it includes the populated places Winterhaven, Ross Corner and Bard.
>Before 1968 I found no source. But probably we can assume that this 
>habit has been permanent. The simplest is to include this area with 
>Arizona, for timezone purposes.

Alois et al.:

I don't presume to advise this community on how or whether such 
unofficial exceptions to time zone observance should be handled 
within the TZ database, but I will pass on my perspective on the 
phenomena - and hope it sheds some light.  In the interest of full 
disclosure let me be clear that my limited knowledge on the topic is 
confined to North American nations and is not authoritative.

Within that small set of nations the US seems to be the only one with 
multiple time zone borders clearly and explicitly defined by an 
acknowledged central authority (the US Dept. of Transportation).  So 
within the US, local unofficial exceptions take on a somewhat 
different context than in some other nations where such central 
control may not be as clearly established, or may not be acknowledged 
by all populations or political subdivisions within the borders of that nation.

I am aware of 8 such exceptions in the US.  Within each, the scope of 
the exception can differ.

To begin with, the actual borders of each such area are rarely 
specified with any clarity or authority.  Winterhaven CA is a bit of 
an exception as the "All American Canal" seems to be locally 
acknowledged as the border, a convenient fixed mapping feature.

Within each exception area one can presume that most businesses and 
residents set their clocks based on the exception, and that 
metaphorically (and literally, if it exists) the clock in town square 
displays the exception time.

But in each area of exception, official time may still have a 
foothold in at least some of these contexts:

The offices and services of City, County, State and/or Federal 
government (e.g. the Post Office).
Law enforcement and judicial services provided by these various 
political subdivisions
Bars/Liquor stores (depending on state law)
Polling places
Cell phones and other mobile consumer electronics that automatically 
adjust local time display

For instance, apparently the automated California state law 
enforcement systems cannot handle multiple time zones.  That would 
make sense as the entire state officially lies within the Pacific 
time zone.  Thus all law enforcement services in Winterhaven follow 
California time, not Arizona time.

And if you are in Pierre SD (which is in the Central time zone) and 
find you have run out of schnapps a little after midnight (when 
off-premise liquor sales are shut down by state law), you can venture 
over the bridge into Fort Pierre - a city and surrounding area that 
unofficially observes Central time despite being in the Mountain time 
zone - and find that the clock in the liquor store is set to Mountain 
time, an hour earlier than the rest of the town.  Your party can continue.

I find no consistent rule of thumb to use to estimate the scope of 
time zone exception observance within each area in question.  Key 
factors seem to be whether the area contains an actual municipality 
(as in Ft. Pierre SD and Phenix City AL), and the degree to which the 
area is governed by a tribal authority.  Other factors are state law, 
law enforcement systems, and simple custom.

In other nations such as Canada and Mexico the scope of exceptions 
can be even more variable, as there may be less authority or 
specificity from a central source.  Within I treat all 
exceptions in Mexico and Canada as official due a general lack of 
clarity or assertion of authority from official sources.  Most 
exceptions in Canada and Mexico have to do with Daylight Saving time 
observance rather than actual time zone borders.

I hope some of this is of use.


Steve Jones 

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