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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?
>
>

   

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