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Well, I think Richard Langley is being a bit lax in his use of language in
suggesting there "is" more than one GMT.  The diffinition has certainly
changed over the years and now GMT has vanished for navigational/techinical
purposes (being replaced by various versions of UT) but it does still remain
at a spoken term (for UCT) and the UK clings to it as the term for official
time in the UK in winter.  To all intents and practical purposes to me (the
time on my watch now) UTC and GMT are the same, being less than a second
adrift.  See:  http://britishsummertime.com/

Also on the subject of the changeover dates these were not always the same
across Europe.  In the UK until 1998 the Autumn change was the day after the
"fourth Saturday" wheras in mainland Europe it was the "last Sunday" in
October; which on several occasions have been different putting France and
the UK (plus the Republic of Ireland, which keeps the same time as the UK)
on the same time for a week.  Since then we seem to be a bit more
co-ordinated.  See: http://www.dti.gov.uk/er/sumtimetb.htm

Paul Bryans

----- Original Message -----
From: "Richard Langley" 
To: 
Sent: Wednesday, November 10, 2004 3:54 AM
Subject: Re: What time is it?


> There is more than one GMT. But when used nowadays, GMT usually refers to
the
> standard zone time kept in the United Kingdom and so is exactly the same
as
> UTC (Coordinated Universal Time). Please read my article
> . A slightly different
> version is available on the Radio Nederland Web site :
> .
> -- Richard Langley
>
> On Tue, 9 Nov 2004, CarlZog wrote:
>
> >The relationship between UTC and GMT is a difference in the source of the
> >measurement of time, and has no bearing on the adoption of "daylight
savings
> >time" conventions, which vary from country to country.
> >
> >UTC, Universal Time Coordinated, is the time derived by numerous atomic
> >clocks (which rely on the frequency of fluctuations of a cesium atom) and
> >adjusted for leap seconds; GMT, or Greenwich Mean Time, is time derived
from
> >the average rate of the earth's movement relative to the sun and adjusted
> >for earth's wobbling on its axis. They are both measured off local
standard
> >time at the prime meridian.
> >
> >For the practical purposes of the vast majority of folks, there is no
> >difference between these two (never more than a second), and, although
the
> >term remains enmeshed in the world culture, GMT is not even actually used
> >anymore as an official source of time.
> >
> >Every 15 degrees of longitude east (-) or west (+) of the prime meridian
> >yields an hour of difference between GMT/UTC and local standard time.
> >
> >In the summer months however, many localities (including most of the
U.S.)
> >abandon standard time for "daylight" time. Merely a product of
convenience
> >for labor,  daylight time is an arbitrary addition or subtraction from
> >standard time. When the change is made is a decision by individual
> >governments that has no reflection on the internationally agreed upon
UTC --
> >which remains constant.
> >
> >Carl
> >
> >----- Original Message -----
> >From: "Jared Sherman" 
> >To: 
> >Sent: Tuesday, November 09, 2004 3:47 PM
> >Subject: What time is it?
> >
> >
> >> No, really. I'm having a moment of confusion over this.
> >>
> >> Nov. 09, 20:42:00 UTC is the same as
> >> Nov. 09, 03:42:00 PM EST
> >>
> >> according to USNO.NAVY.MIL, and they should know. But I thought there
was
> >> no
> >> daylight savings time correction to UTC, and "EST" is "Eastern Saving
> >> Time"
> >> (clocks moved an hour behind real time) in the eastern US now.
> >>
> >> Or, is this another instance of a difference between GMT and UTC, where
> >> UTC
> >> changes but GMT doesn't?
> >>
> >> Can someone unconfuse me on how US times, UTC, and GMT all do or don't
> >> vary
> >> with Daylight Slavings Time?
> >>
> >>
> >
>
>
>
============================================================================
===
>  Richard B. Langley                            E-mail: lang@unb.ca
>  Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
>  Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142
>  University of New Brunswick                   Fax:      +1 506 453-4943
>  Fredericton, N.B., Canada  E3B 5A3
>      Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/
>
============================================================================
===

   

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