The opportunity of leap seconds

From: Rob Seaman <>
Date: Sat, 7 Jan 2006 10:38:02 -0700

On Jan 7, 2006, at 8:02 AM, Poul-Henning Kamp wrote:

> I have no problems with different timescales for different purposes.

Great! Consensus reached!

Rejoicing in all the lands! May one suggest a parade in
celebration? The great Parade of the Leap Seconds! To be held on
December 31 or June 30 as the spirit moves us (or January or July 1,
for those east of Greenwich.) Now, what would that be in French? La
Parade du Saut de Seconde?

> For instance I very much wish the Astronomers would start to use
> UT1, which is very much "their" timescale, and stop abusing UTC,
> which isn't, as a "convenient approximation".

...ohhhh - should have stopped while you were ahead.

Astronomers use UT1. Astronomers use UTC. Astronomers are among the
biggest users of TAI and GPS and likely any other timescale you care
to name. Our community cares deeply about time. How precisely does
this disqualify us from participating in the process?

By your logic, the U.S. Surgeon General should be a chiropractor.

> Civil time is in the hands of individual governments, and they tend
> to expect their computers to use the same time as the rest of their
> country.

The proper response to this comes down to us from the staid and
proper British, inheritors of the immortal legacy of Shakespeare and

        Bollocks! (

We can incessantly debate trivialities, or we can seek a grand vision
of the shared meaning of time in human concerns.

I presume everybody here is competent to perform the conversions
between different local clocks. Some have been instrumental in the
construction of new systems of time for manifold scientific,
technical and civil purposes. The following assertion thus falls flat:

> Nobody here is in any position to do anything about civil time or
> legal time, neither are we in a position to introduce a "computer
> time scale" in a pathetic attempt to paste over leap seconds.

Geez! Cut the guy a break for coming late to the discussion. For
his first posting, he has already elucidated a central issue of the
debate. Would be nice if the ITU were debating the issues raised by
Kuhn and Sokolov, rather than engaging in the political shenanigans
you appear to applaud.

...but your upbeat speech has won my vote if you choose to run for
student body president.

For six years we've pretended that Coordinated Universal Time, and
thus the concept of a leap second, is some extremely complicated
issue of import only to technical wonks like us. Balderdash. It's
fine if you want to challenge my definitions for particular terms.
Fine, fine, fine. So instead of "Civil Time" and "Solar Time", slap
new names on my definitions:

        Canoli = common basis for diverse time usage worldwide
        Eclair = baseline representation of Earth orientation

Unless we *completely* change our notion of Canoli, Canoli is tightly
constrained to follow Eclair simply by the fact that today and
tomorrow and the million days that follow are all required to be dark
at night and light in the day. Whether we choose to bleed off the
daily accumulating milliseconds one second or 3600 at a time, bleed
them we must...and even people who loathe the very notion of leap
seconds admit this. (The craven ITU proposal is obligated to pay lip
service to leap hours, though what they really are saying is "let's
close our eyes and wish it away".) Time to move on.

Or another analogy: Canoli is an arrow, Eclair its target. Canoli
can be arbitrarily small, Eclair arbitrarily distant. Canoli is
constrained to fly straight, thus an arbitrarily small choice of
aiming options will result in hitting Eclair.

Or consider the network time protocol. NTP can update the local
clock on an arbitrary schedule. Two popular choices are daily on the
one hand and "continuously" on the other. I suspect we dastardly
astronomers are not alone in preferring the latter (small, frequent,
fractional "leaps") rather than the former (large, rare, colossally
arbitrary jumps).

Rob Seaman
National Optical Astronomy Observatory
Received on Sat Jan 07 2006 - 09:38:24 PST

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