Re: [LEAPSECS] Leap second status?

From: Markus Kuhn <Markus.Kuhn_at_CL.CAM.AC.UK>
Date: Thu, 28 Nov 2002 15:14:10 +0000

Rob Seaman wrote on 2002-11-27 23:35 UTC:
> > This Colloquium is anticipated to be the final opportunity for
> > gathering information toward drafting a recommendation to the ITU-R.
> Not excellent! The world is to get one and only one opportunity to
> comment - and this is only to occur *before* a recommendation is
> provided for anybody to comment on?

I agree. What troubles me about the process is that so far there hasn't
been any specific proposal (or even a small named set of finalist
alternatives) been published that can be discussed in public.

Where is the web site that lists the proposed options under discussion?

I have seen some frighteningly drastic ideas (such as detaching the
definition of civilian time entirely from the rotation of the earth),
without any detailed rational for why that would be needed. I have also
seen some rather irrational explanations (such as obscure undocumented
software problems with one particular satellite navigation system) being
floated, that make no sense technically to me but have repeatedly been
quoted as a primary reason for the need to modify civilian time (UTC).

I am well familiar with the problems that today's UTC can cause, but
overall, I am convinced that today's definition of UTC is already very
close to the optimal compromise and that it needs no major tinkering.
Therefore, I strongly hope that the idea of dramatically redefining UTC
will just disappear.

For many of the problems that are often quoted in relation to UTC, the
appropriate solution can often be

  a) Better engineering and fixes to fielded systems that have
     problems at the moment with UTC.

  b) Better availability of TAI and TAI-UTC change warning in
     time-signal dissemination stsrems.

  c) Additional standards that provide guidence for the implementation
     of systems where the current definition of UTC might cause
     minor difficulties, on how to circumvent these problems.

As an example for solution c), I have proposed here several times over
the past two years the standardization of a smoothed variant of UTC
(which I nicknamed UTS) for use by application program interfaces and
communication protocols in networked computers:

(Warning: the text is already written in the classic undigestable style
of an ITU-R resolution, so please read it very carefully twice before
forming an opinion.)

UTS has in various online discussions been welcomed by leading
distributed computer systems timekeeping experts as a highly practical
and useful way around many of the problems that a naive use of UTC in
computer systems can cause. At the same time the adoption of UTS as an
international standard does *not* need any modification to the
definition of UTC and usually no modification to the way in which UTC is
disseminated today, because UTC and be converted into UTS locally by the
receiver of time synchronization signals. [The only modification that
UTS encourages to time services is that every UTC disseminating service
should warn about forthcoming leap seconds at least an hour in advance.
Most do this already, but some (e.g., Britain's MSF transmitter) ought to
be upgraded to have that capability, in order to enable receivers to do a
reliable UTC->UTS conversion without any additional maintenance of
leap second tables].

UTS was my attempt to use the invitation to make constructive
contributions on this mailing list, but I haven't heard *any* reply from
ITU-R on this at all. So is this mailing list just a waste of my time,
and someone will nevertheless claim later that there was some public

Even if ITU-R is not interested in UTS (why?), then it would still be
very helpful if I got a definitive reply on this mailing list that says
so. I would then approach other standards bodies with a greater
relevance in information technology (ISO, IETF and ECMA for example)
with this proposal.

Best regards,

Dr Markus Kuhn
University of Cambridge
Computer Laboratory
15 JJ Thomson Avenue
Cambridge CB3 0FD
United Kingdom

Phone: +44 1223 3-34676
Fax: +44 1223 3-34678
Received on Thu Nov 28 2002 - 07:22:38 PST

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