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Groups > comp.lang.python > #64948
| From | Grant Edwards <invalid@invalid.invalid> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: pytz question: GMT vs. UTC |
| Date | 2014-01-29 19:02 +0000 |
| Organization | PANIX Public Access Internet and UNIX, NYC |
| Message-ID | <lcbj8s$f6n$1@reader1.panix.com> (permalink) |
| References | <mailman.6092.1391016578.18130.python-list@python.org> |
On 2014-01-29, Skip Montanaro <skip@pobox.com> wrote:
> According ato the pytz doc (http://pytz.sourceforge.net/):
>
> "UTC is Universal Time, also known as Greenwich Mean Time or GMT in
> the United Kingdom."
>
> If they are equal,
The question is _are_ they equal?
There is an exact defintion for what "UTC" is, and there's another
exact definition of what UT1 is (more about this later). Civil
timezones are defined as offsets from UTC.
It seems that "GMT" no longer has an exact definition (at least from a
metrologist's perspective) can be used to mean either UTC or UT1. UTC
and UT1 can differ by up to 1 second. Leap seconds are occasionally
added to UTC to keep it from drifting more than 1 second from UT1.
From a metrology point of view, what was originally called "GMT"
(solar time at 0 degrees longtitude) is now called "UT1". So some
people rightly claim that "GMT" means UT1. But nobody actually _uses_
UT1 (except metrologists and astronomers).
All civil time is based on UTC: the official time in Greenwich (except
during BST) is not UT1, it's UTC. So some other people rightly claim
that "GMT" refers to UTC.
In a software libary context, I would say that GMT should mean UTC and
they ought to be considered equal and should always produce identical
results. In a metrology context, people saying "GMT" probably ought
to be smacked across the knuckes with a 12-inch platinum-iridium ruler
and asked to try again until they specify either UTC or UT1 (or some
other precisely defined UT-flavor).
http://en.wikipedia.org/wiki/Universal_Time
--
Grant Edwards grant.b.edwards Yow! A dwarf is passing out
at somewhere in Detroit!
gmail.com
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pytz question: GMT vs. UTC Skip Montanaro <skip@pobox.com> - 2014-01-29 11:29 -0600
Re: pytz question: GMT vs. UTC Grant Edwards <invalid@invalid.invalid> - 2014-01-29 19:02 +0000
Re: pytz question: GMT vs. UTC Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-01-29 19:17 -0500
Re: pytz question: GMT vs. UTC Chris Angelico <rosuav@gmail.com> - 2014-01-30 11:28 +1100
Re: pytz question: GMT vs. UTC Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-01-29 20:50 -0500
Re: pytz question: GMT vs. UTC MRAB <python@mrabarnett.plus.com> - 2014-01-30 02:40 +0000
Re: pytz question: GMT vs. UTC Chris Angelico <rosuav@gmail.com> - 2014-01-30 14:27 +1100
Re: pytz question: GMT vs. UTC wxjmfauth@gmail.com - 2014-01-30 00:45 -0800
Re: pytz question: GMT vs. UTC MRAB <python@mrabarnett.plus.com> - 2014-01-30 11:51 +0000
Re: pytz question: GMT vs. UTC Grant Edwards <invalid@invalid.invalid> - 2014-01-30 15:21 +0000
Re: pytz question: GMT vs. UTC Dan Sommers <dan@tombstonezero.net> - 2014-01-31 04:08 +0000
Re: pytz question: GMT vs. UTC Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-01-31 04:37 +0000
Re: pytz question: GMT vs. UTC Dan Sommers <dan@tombstonezero.net> - 2014-01-31 06:28 +0000
Re: pytz question: GMT vs. UTC Chris Angelico <rosuav@gmail.com> - 2014-01-31 17:42 +1100
Re: pytz question: GMT vs. UTC Dan Sommers <dan@tombstonezero.net> - 2014-02-01 06:30 +0000
Re: pytz question: GMT vs. UTC Roy Smith <roy@panix.com> - 2014-01-31 10:00 -0500
Re: pytz question: GMT vs. UTC Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-01-31 09:59 +0000
Re: pytz question: GMT vs. UTC Pete Forman <petef4+usenet@gmail.com> - 2014-02-02 12:45 +0000
Re: pytz question: GMT vs. UTC wxjmfauth@gmail.com - 2014-02-02 06:38 -0800
Re: pytz question: GMT vs. UTC Grant Edwards <invalid@invalid.invalid> - 2014-02-02 16:03 +0000
Re: pytz question: GMT vs. UTC Rustom Mody <rustompmody@gmail.com> - 2014-01-30 23:02 -0800
Re: pytz question: GMT vs. UTC wxjmfauth@gmail.com - 2014-01-31 02:17 -0800
Re: pytz question: GMT vs. UTC Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-01-31 14:50 +0000
Re: pytz question: GMT vs. UTC Roy Smith <roy@panix.com> - 2014-01-31 10:04 -0500
Re: pytz question: GMT vs. UTC Robert Kern <robert.kern@gmail.com> - 2014-01-31 15:08 +0000
Re: pytz question: GMT vs. UTC Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-01-30 19:44 +1300
Re: pytz question: GMT vs. UTC Christian Heimes <christian@python.org> - 2014-01-30 10:49 +0100
Re: pytz question: GMT vs. UTC wxjmfauth@gmail.com - 2014-01-30 02:10 -0800
Re: pytz question: GMT vs. UTC Grant Edwards <invalid@invalid.invalid> - 2014-01-30 15:23 +0000
Re: pytz question: GMT vs. UTC Larry Martell <larry.martell@gmail.com> - 2014-01-30 10:28 -0500
Re: pytz question: GMT vs. UTC Chris Angelico <rosuav@gmail.com> - 2014-01-30 21:10 +1100
Re: pytz question: GMT vs. UTC Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-01-30 20:18 -0500
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