Re: [LEAPSECS] Accommodating both camps

From: Warner Losh <imp_at_BSDIMP.COM>
Date: Wed, 25 Jan 2006 10:34:41 -0700 (MST)

From: Michael Deckers <>
Subject: Re: [LEAPSECS] Accommodating both camps
Date: Wed, 25 Jan 2006 16:50:59 +0000

> Poul-Henning Kamp wrote on 2006-01-25:
> > If we abandon leapseconds today to avoid getting computer problems,
> > we still have several hundred years of time to decide how to
> > deal with any long term effects.
> I do not think so. When civil time is no longer connected to solar
> time (which is more than abandoning leap seconds!),

I don't understand your statement here. Can you elaberate?

> then this affects
> legal and cultural issues all over the world, and a difference of a
> minute or so may well be relevant. Such a difference can accrue
> in 60 or 80 years.

I have a hard time believing that 1 minute would be significant from a
cultural point of view, when 1 hour of daylight saving time isn't
significant at all. I have a hard time believing that 1 minute would
make a difference when the deviation from mean solar time is +- 1/2
hour (or more) in most time zones. Since 1960 (call it 45 years),
we've had a divergence of 33 seconds between TAI time and UTC time, so
the 60-80 year time frame seems reasonable.

This is the biggest misunderstanding that I have with people that make
a big deal out of no longer being on solar time. We already have a
huge tolerance for the difference between local solar time and legal
time, given the 15 degree time zones. I have yet to meet anybody in
Denver that cares that our solar noon is off a bit (being at ~105
degrees west, it is pretty close), or that there appears to be a
seasonal variation on the order of 10 minutes in the observed time of
solar noon, and the mean solar noon time at the extremes of the year.
In addition, while Denver is on Mountain Time, most of Mexico, which
is directly south of Denver, is on Central Time, having seemly chosen
to be an hour off of solar time.

See for information on solar
time vs mean solar time. See for some
background om time zones and daylight saving time.

> I am not just thinking of lawyers trying to exploit the difference
> between legal time in Britain (which is GMT) and the time scale
> disseminated by the NPL. What I find much more disquieting is first,
> that some problems may become apparent only very late, when the difference
> between TI and UT is large enough, and, secondly, that it appears to
> be very difficult to say which areas of daily life will be affected.

We already have a > 30 second difference between TAI and UTC time.

> On the other hand, I believe that most if not all of these problems
> will not be life-threatening -- whereas many of the problems with
> leap seconds and computers may well be. So this, rather than other
> technical merit may finally decide the question. But again, giving up
> leap seconds in UTC is not the same as accepting atomic time as civil
> time.

Again, I don't quite understand this statement. Can you elaberate a
bit on the difference?

Received on Wed Jan 25 2006 - 09:39:15 PST

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