In article 008d01c9a78b$6f7374a0$9d83e262@newiw112a268qp, Rich and
Marcia Putz rputz@bnin.net writes

Yes, I think you'll find that offset is the difference between Greenwich
Mean Time and Paris Mean Time.

Before the international conferences that defined time all over the
world in terms of GMT and integer (mostly) offsets therefrom, France
would have been using Paris as their Prime Meridian - natural enough,
every nation assumes it's capital is the centre of the world, the hub of
the universe.

Although what a country that has a large extent in longitude (e.g. the
USA or USSR) would do in this case, I am unsure.

--
Geoff Powell

I don't have reference at hand but a long time ago there was a lot of
national meridian references, but I think they disappeared by WWI or WWII in
favor of the "International Meridian" in Greenwich. I agree that there was a
Paris meridian (it is still engraved on a building of Paris Observatory, as
well as San Fernando (Andalucia, Spain) was the reference meridian for
Spain, etc.
As far as I know, Poland legal time is defined by UTC(PL), for USA, I'm not
sure if it's UTC(USNO) or UTC(NIST), I believe that Germany is UTC(PTB);
I'm surprised that the legal definition for UK is GMT, since there was an
argument from British people that they cannot agree to suppress leapseconds
in UTC without going to Parliament to change the definition for UK legal
time. Any more insights ?
Have a nice day,
Jean-Louis Oneto
----- Original Message -----
From: "Rich and Marcia Putz" rputz@bnin.net
To: time-nuts@febo.com
Sent: Wednesday, March 18, 2009 5:35 AM
Subject: [time-nuts] French Time offset

On 3/17/09 10:35 PM, "Rich and Marcia Putz" rputz@bnin.net wrote:

Paris is at 2degrees 20 min longitude, which isn't enough to account for
12.5 minutes.  Sevres (where BIPM is) is actually a bit to the west, so even
less solar time difference.

BIPM is an international organisation, and apart to be in France, has
nothing to do (and never had as far as I know) with the definition of French
legal time. At least no more than for any other country UTC (or TAI) based.
Jean-Louis
----- Original Message -----
From: "Lux, James P" james.p.lux@jpl.nasa.gov
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Wednesday, March 18, 2009 12:58 PM
Subject: Re: [time-nuts] French Time offset

Just casting about for potential meridian locations that might explain the 12.5 minute difference. Maybe the central longitude of France is 12.5 minutes(of time, 3 1/8th degrees of longitude) from Greenwich? (like India's time zone being on the half hour). Things get done for funny reasons: After all, the physical size of France is why ATM "cells" (packets) are 53 bytes (48 byte payload) instead of either 32 byte or 64 byte payloads.

9 min 20 sec = 9.333 mins = 0.155 hours = 2.33 degrees of longitude = 2 deg 20 min longitude = longitude of Paris

Which makes sense.. The article actually talks about France defining GMT in terms of PMT.

Jim

Lux, James P skrev:

If you look at the map Arnold linked to, you will see that France sits
very neatly into the Zulu-timezone. Infact, France is better served by
it then GB. I have enjoyed the incorrectness of France time-zone-wise on
my many travels to France, so I am not complaining from a practical
point of view, but it would not be my first choice if I would choose
something for France.

Map:
http://media4.obspm.fr/public/amc/images/mesure-temps/images/849.gif

Cheers,
Magnus

Phil,

phil skrev:

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

And what about Spain, which is mostly WEST of 0 longitude, yet is on UTC+1

----- Original Message -----
From: "Magnus Danielson" magnus@rubidium.dyndns.org
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Wednesday, March 18, 2009 7:20 PM
Subject: Re: [time-nuts] Time offset

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.

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.

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.

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.

Phil

phil skrev:

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.

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.

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.

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

M. Warner Losh skrev:

Warner has understood my quest here...

It would be an interesting development if countries left UTC for say UT2
as their official time if leap seconds would cease. It would effectively
make the change of leap second policy cause UTC a less and less valuable
source. I am becoming more and more sceptical to the wisdom of dropping
the leap seconds or at least leap mechanism.

It may be OK with current UTC and it may not. UTC may cease to be a
reasonable interpretation if leap seconds ceases.

Exactly.

The nitty gritty details...

Cheers,
Magnus

Has anyone thought of making some huge rockets and attaching them to
the Earth at the Equator in such a way that when they are fired, we
could speed-up the World so its rotation is exactly 24 x 60 x 60 x
9,192,631,770 cycles of the radiation, which corresponds to the
transition between two hyperfine energy levels of the ground state of
the 133Cs atom per day.. That way we could forget about adding leap
seconds. We could even speed it up sufficiently to catch-up on the
leap seconds that have already been inserted and then we could remove
them. All we would have to do in the future would be to give the Earth
an accasional kick to keep it's speed constant and never have to
agonise over the insertion of leap seconds in the future. Now wouldn't
that make life simpler.

Do I have to add the smiley?

73,
Steve

2009/3/19 Magnus Danielson magnus@rubidium.dyndns.org:

--
Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW
Omnium finis imminet

In message 1231b6a80903190341x362ae5cfg8651f1d36fc176fc@mail.gmail.com, Steve
Rooke writes:

Yes, I did a back of the envelope calculation, besides the practical
issues, you really cannot afford to do that.

A better strategy, seen from an economy of energy and resource point
of view, would be to change the orbit of the moon by nudging some
asteroids into it

You would have to get it to leave the earths orbit and slingshot around
venus (or mars), then come back and go into orbit the opposite way.

Some side-effects must be expected.

Poul-Henning

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

I asked one of NPL's senior scientists in the T&F Dept about GMT.

His reply is as follows:-

"" There is no current formal definition of GMT as far as I am aware.
Greenwich Mean Time is of course loosely defined as "the mean solar time of
the Greenwich meridian", where the meridian has been marked since 1884 by
Airy's transit telescope. It is an astronomical time scale, in which the
length of the second and the scale epoch is adjusted frequently to remain in
step with the astronomical observations. It is debatable whether GMT can be
determined to much better than the 100 ms level.

GMT was formally renamed Universal Time (UT) in 1928 although the previous
name remained in widespread use particularly in English-speaking countries.
In the 1950s various modified forms of UT were defined: UT0, UT1 and UT2,
which could differ by up to 35 ms. UT1 is the only one which is still
measured and disseminated, although several changes to its definition have
made it a measure of Earth rotation rather than mean solar time.

UTC is of course a post-processed atomic time scale with its scale interval
based on the SI second and leap seconds inserted when necessary to keep it
within 0.9 s of UT1. UTC(NPL) is one of the national realisations of UTC,
and is in practice the reference time scale for the UK. It is therefore
incorrect to say that UTC [or UTC(NPL)] is GMT. However, UTC does provide a
practical realisation of "GMT" at the 1 second level. This is the argument
used by the UK government for not yet changing references to time in UK laws
from GMT to UTC: the distinction between the two only becomes important when
time stamps are required to an accuracy better than 1 second, which is still
generally not the case. ""

Rob Kimberley

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Magnus Danielson
Sent: 19 March 2009 09:29
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Time offset

M. Warner Losh skrev:

Warner has understood my quest here...

It would be an interesting development if countries left UTC for say UT2 as
their official time if leap seconds would cease. It would effectively make
the change of leap second policy cause UTC a less and less valuable source.
I am becoming more and more sceptical to the wisdom of dropping the leap
seconds or at least leap mechanism.

It may be OK with current UTC and it may not. UTC may cease to be a
reasonable interpretation if leap seconds ceases.

Exactly.

The nitty gritty details...

Cheers,
Magnus

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