[LEAPSECS] Looking-glass, through

[Warner Losh]

On 01/12/2011 13:48, Clive D.W. Feather wrote:

> Rob Seaman said:

>> For instance, what authority will historians or lawyers consult to learn the applicable timezone offsets that were in force in some location(s) during some epoch(s) in question?

> <FX: falls about laughing>

>

> Those of us on the timezone list can't even find out this information for

> this year for many places. It's almost impossible to determine it for (say)

> 200 years ago for almost anywhere.


That wasn't standardized until the 1850's in the US with the advent of 
railroads.  Good luck determining it from extant historical records.  
The Timezone database is about as good as it gets, and it is horrible 
for anything prior to 1990 (no offense guys) if you want more than a 
vague idea of something that might be right.  It won't tell you that 
Chaffee County Kansas moved from the Central Time Zone to the Mountain 
Time Zone in 1963, but might tell you if it did in 1983.  Just read 
through it for different city entries, especially those in Europe that 
have changed hands many times this century...

Or lookup February 30th on wikipedia sometime for how there once was a 
double leap year in Sweden to get them aligned with the new Gregorian 
Calendar.

Time keeping, and even calendar keeping, in the past was a huge 
hodge-podge of gunk that only got straightened out most places in the 
20th century.


> This is *nothing* to do with what the underlying time scale is. Tony has it

> right: you have things completely backwards.


Agreed.  Civil time is de-facto based on what is convenient.  Laws were 
meant to codify the time products that were available at the time they 
were enacted, not enshrine some bizarre way of doing things.  The US has 
been de-facto UTC since the 1970's, even though the law didn't catch up 
with the facts on the ground until just a couple of years ago.

Warner