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From: Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid>
Newsgroups: comp.lang.javascript
Subject: Re: ISO 8601 Code Review Wanted
Date: Fri, 23 May 2014 20:44:07 +0100
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In comp.lang.javascript message <b8grn9ddh5slf5ml2u9hmd8s88v4f2frea@4ax.
com>, Thu, 22 May 2014 10:20:56, John Harris
<niam@jghnorth.org.uk.invalid> posted:

>On Wed, 21 May 2014 17:30:57 +0100, Dr J R Stockton
><reply1400@merlyn.demon.co.uk.invalid> wrote:
>
>  <snip>
>>GMT is required, in civil life, probably only in the UK and the Crown
>>Dependencies.  UK law requires GMT / GMT+1, but UK implements it with
>>UTC.  GMT is not the same as UTC.  UTC applies everywhere on Earth,
>>though anyone/anything moving at relativistic speeds may have trouble
>>with it.
>
>With time measurement accurate to 1 part in 10^15, 'relativistic' must
>be pretty slow these days. 2 mph ? (or is my mental arithmetic wrong?)

About right, anyway.  But, although JavaScript can measure time to about
that accuracy, it can only do so over that number of milliseconds.

>>But JavaScript cannot handle UTC, since it does not know about
>>leap seconds - it uses imprecise GMT.
>  <snip>
>
>Rather than imprecise GMT say it uses AT (Atomic Time).
>(Note : UTC is AT with a changing offset to keep UTC in step with the
>irregular earth's rotation).

I used "GMT" because everyone knows what they think it means, but most
people think is AT is used to keep Vienna in.  AT is not in
<http://stjarnhimlen.se/comp/time.html>.  H'mmm - an At or Att is a
centi-Kip.  Perhaps you mean TAI.

But JavaScript does not use TAI, as there is no common mechanism for
disseminating TAI to computers running JavaScript.  In practice,
JavaScript is generally intermittently synchronised to UTC, and cruises
in a GMT-like manner in between.

-- 
 (c) John Stockton, nr London, UK.   E-mail, see Home Page.    Turnpike v6.05.
 Website  <http://www.merlyn.demon.co.uk/> - w. FAQish topics, links, acronyms
 PAS EXE etc. : <http://www.merlyn.demon.co.uk/programs/> - see in 00index.htm
 Dates - miscdate.htm estrdate.htm js-dates.htm pas-time.htm critdate.htm etc.