[PW] Historical time zones in the US

brian whatcott betwys1 at sbcglobal.net
Tue Aug 23 11:21:50 PDT 2016


Nit-picking here: Gary mentioned setting local mean time by reference to 
the local meridional crossing of the Sun. He did not mention doing this 
EVERY day. Local mean time and solar time  are connected by the equation 
of time.

Brian W

On 8/22/2016 4:34 PM, Anton Sherwood wrote:
> On 2016-8-21 15:31, Gary Lee Phillips reported that the two cities of 
> Bristol
>> Have both followed the same time zone changes since November 18, 1883
>> when standard time was first instituted in the US. Prior to that, both
>> towns used local mean time determined by setting noon to match the time
>> when the sun crosses due south.
>
> If it was set by the sun each day, that's not mean time.  The 
> difference between mean time and sundial time varies by half an hour 
> over the year.  https://en.wikipedia.org/wiki/Equation_of_time
>
> The definition of mean time is rather interesting; see 
> https://en.wikipedia.org/wiki/Solar_time#Mean_solar_time
>



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