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    Re: What time is it?
    From: Richard B. Langley
    Date: 2004 Nov 9, 23:54 -0400

    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.
    >----- Original Message -----
    >From: "Jared Sherman" 
    >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---.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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