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

From: Poul-Henning Kamp <>
Date: Thu, 19 Jan 2006 21:53:23 +0100

In message <E1EzgPT-00022K-00_at_alva.home>, Tim Shepard writes:
>> 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?

As long as the corrections are of the small magnitudes we have seen
(10e-12 and below) and as long as they are applied to both TAI and
UTC at the same time, I have no trouble with them.

The reason I say 10e-12 is that only high end cesium and hydrogen
units are affected by that in practice, everybody else can just
ignore it.

Remember, we can also risk other fundamental units needing an adjustment,
the kilogram being in the high risk bracket here.

>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 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.

But the half second delta to UTC is also a non-starter.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Received on Thu Jan 19 2006 - 13:03:42 PST

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