[time-nuts] Time offset

Magnus Danielson magnus at rubidium.dyndns.org
Thu Mar 19 05:19:39 EDT 2009


phil skrev:
> ----- Original Message ----- 
> From: "Magnus Danielson" <magnus at rubidium.dyndns.org>
> To: "Discussion of precise time and frequency measurement" 
> <time-nuts at febo.com>
> Sent: Wednesday, March 18, 2009 7:20 PM
> Subject: Re: [time-nuts] Time offset
> 
> 
>> Phil,
>>
>> phil skrev:
>>> Magnus,
>>>
>>> The most comprehensive collection of time offset data and reference to 
>>> each
>>> countries latest laws might be found at:
>>> http://www.twinsun.com/tz/tz-link.htm
>> As far as I can see, it works under assumption that GMT = UTC. Thus, it
>> fails on my lackmus test of GMT+1h for Denmark.
>>
>> While it is a great resource, if fails this fine distinction that I was
>> asking about.
>>
>> Cheers,
>> Magnus
> 
> Magnus,
> On that same page was a link to an older archive, tzarchive.gz 
> ftp://elsie.nci.nih.gov/pub/tzarchive.gz
> 
> You will find references to actual laws and links imbedded in that for 
> various countries. Your assumption that that GMT = UTC I would say is true 
> from 1970 on.

I do not assumed GMT = UTC, I said the page assumes it by the look of 
things. I have not looked into that file in particular, will do.

> GMT was the first internationally accepted international/global standard 
> with various "legally" defined offsets. It was only after the advent of the 
> cesium and the gps system that UTC became the standard, again with the legal 
> offsets. Most older law, pre 1970 I've seen references to gmt, but when laws 
> are appended for example saving time, reference is often or sometimes made 
> to utc, though the old legal definition may still reference gmt.
> 
> Perhaps most lawmakers accept them (gmt, utc) to be the same with their 
> local/regional offsets now that you can get standardized utc off satellites 
> world wide.

The trouble is that many thinks that UTC is just the new name for GMT, 
but I can write GMT as they are the same. The EC translators does think 
like that for instance, so the same text can read UTC or GMT depending 
on which language you read it in.

The point there being, there is an educational problem among those 
handling legislation that GMT and UTC is two distinct things.

> Other than the "flying clock" how else can all countries of the world 
> synchronize their time? I think a lot of small countries have a single 
> cesium, if that, tied to gps and vend their countries "official" time based 
> on that. In that case they are based on UTC regardless of the wording of 
> their prior law.

You definitly should read up on history since ground-based transmitters 
have been used to compare between laboratories since the 1940ies at 
least. The flying clock allowed a very nice complement as it allowed the 
removal of time-bias which could only be estimated.

> I know in North Carolina, USA a law was still on the books a few years ago 
> that it was illegal to look at your wife naked. Law is often slow to catch 
> up with society and technology. The various countries definitions of time 
> referencing GMT may too be laws that have not come into the twentieth 
> century though utc (with offsets) is now the accepted standard.

This is indeed one problem, the other being that they have incorrect 
writing even if the intent was correct.

The Danish law is the oldest still acting law that I know of from the 
top of my head, but then I havent read many of them.

Cheers,
Magnus




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