[ntp:questions] Leap second functional question

Kevin Oberman oberman at es.net
Sat Feb 23 00:02:49 UTC 2008


> Date: Fri, 22 Feb 2008 17:55:04 -0500
> From: Danny Mayer <mayer at ntp.isc.org>
> Sender: questions-bounces+oberman=es.net at lists.ntp.org
> 
> 
> David Woolley wrote:
> > Evandro Menezes wrote:
> > 
> >> Aren't you confusing UTC and GMT?  Or maybe I'm the one confusing
> >> both...
> > 
> > Nearly everyone confuses UTC and GMT.  GMT is an obsolete name for UT1, 
> > or something close, but the BBC still uses it to, incorrectly, mean UTC.
> 
> That's actually not true. GMT exists in the UK as the local time zone 
> reference name. GMT was renamed UTC for mostly political reasons. GMT 
> follows UTC but it isn't an incorrect reference.

Are you really sure? I've always read that GMT is UT1, not UTC. I just
read the article on wikipedia and it seems to agree that GMT is UT1.

Of course, UT1 is always within 1 second of UTC.

In any case, the definitions in the various Wikipedia articles (UTC, UT,
and GMT) all agree with what I learned dealing with timing issues in the
past, although both those folks (the ones in Boulder, Colorado) and
Wikipedia could be wrong.

The article also states that UTC does not always have 86,400 seconds in a
day, although POSIX specifies that a day is always 86,400 seconds long.

If anyone can provide a reference from one of the real standards
specifications, I would appreciate it. (If it does not match with the
information I have received form the NIST folks in Boulder, I'll be very
surprised.)
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751
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