# Re: [LEAPSECS] Internet-Draft on UTC-SLS

From: Tim Shepard <shep_at_ALUM.MIT.EDU>
Date: Thu, 19 Jan 2006 15:29:31 -0500

> The serious timekeeping people gave up on rubberseconds in 1972 and
> I will object with all that I can muster against reinventing them
> to paste over a problem that has a multitude of correct solutions.

As I learned from a recent posting to this mailing list, it seems that
even TAI has rubber seconds (adjustments to the rate is made from time
to time to compensate for errors that have been accumulating, making
TAI a better (more useful) approximation time).

Do you object to those adjustments (rubber seconds) to TAI as well?

If so, then what are we to do? (Even two atomic clocks will not run
at exactly the same speed, and something must be done to cope with the
fact that they will drift apart.)

regarding the size of changes to the rate of a second of TAI? Is it
one ppm, 100 ppb, 10 ppb, 1 ppb, 10^(-10), 10^(-11), 10^(-12), or *what*?

> > "Coordinated Universal Time with Smoothed Leap Seconds (UTC-SLS)",
> > Markus Kuhn, 18-Jan-06. (36752 bytes)
> >
> > http://www.ietf.org/internet-drafts/draft-kuhn-leapsecond-00.txt

This draft bugs me a bit because it changes the length of a second (as
seen by its clients) by a rather large amount (a thousand ppm).

A change in rate of one ppm would not bother me, but that would take a
bit more than 11.5 days to accomplish the change.

A change in rate of ten ppm could accomplish the phase change with
less than 1 day's warning before the UTC leap second insertion if
accomplishing it could be split between the 50,000 seconds before UTC
midnight and the 50,000 seconds after UTC midnight.

Hmm....
-Tim Shepard
shep_at_alum.mit.edu
Received on Thu Jan 19 2006 - 12:40:42 PST

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