[tz] New 'Theory' section "Accuracy of the tz database"

Zoidsoft zoidsoft at gmail.com
Tue Sep 17 05:16:48 UTC 2013

PS - I recently moved back to Pulaski, NY and I had a conversation with a
real estate broker and he said that there were 42 Amish families now
living in the Pulaski area (When I was born I knew of none).  They don't
appear to observe DST because their horse drawn carriages (which are nearly
as ubiquitous as cars around here) which go by every morning taking their
kids to school by the cemetery did not keep up with the shift in DST
(according to my father).  Given their lack of electricity I'm not even
sure they have clocks.  This kind of political division is another
dimension that divides not by boundaries on a map, but by who is keeping
the clocks.

On Tue, Sep 17, 2013 at 12:45 AM, Zoidsoft <zoidsoft at gmail.com> wrote:

> The ACS Atlas would give a clue as to how many would be needed;
> approximately 2000 zones in the Olson format would be needed to match what
> is in the ACS atlas and it isn't really "complete".  The mapping of time
> zones appears mathematically to be like a logarithmic spike with one end
> toward relative uniformity (around 400 zones on the low end after 1970) and
> the other end to where each clock has its own unique time zone history (aka
> LMT).  It is a matter of where you want to draw the line.  The farther in
> the past you go toward the date of onset of standard time or LMT the more
> chaotic it gets (to the point where it simply would be impossible to have
> certainty for many locations).
> Due to the fact that most people reside in cities, ACS went about as far
> as reasonably possible given the limited manpower.  It was no doubt an
> extremely tedious task, but I do wish that they had made their research
> methods and criteria for selecting daylight transitions public.  As the
> data currently stand, my confidence in transition times for DST for dates
> in the first half of the 20th century is shaky at best.  I only feel
> relatively confident if it is near the dead of winter or the height of
> summer for this period in history.
> On Mon, Sep 16, 2013 at 9:32 PM, Paul Eggert <eggert at cs.ucla.edu> wrote:
>> Lester Caine wrote:
>> > why would there be 'thousands' of new timezones?
>> Because, if one defines a "region" to be "a set of geographical
>> locations where civil-time clocks have agreed since standard time
>> was introduced", there must be thousands of such regions, each
>> unique as far as UT-offset history goes.  Shanks identifies
>> over 300 such regions for Indiana alone, and most likely he
>> missed some.  (Again, I'm ignoring UT offset before standard time
>> was introduced, and I'm ignoring the date of transition to standard
>> time.)
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