Re: [LEAPSECS] The real problem with leap seconds

From: Poul-Henning Kamp <>
Date: Sat, 07 Jan 2006 21:20:33 +0100

In message <20060107192023.GM2021_at_feynman>, Neal McBurnett writes:

>> 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.
>Yes again. And they are free to choose TAI if they want a uniform
>time scale. But why take the choice of a UTC that remains within 0.9s
>of the earth's average rotation rate?

Well, the BIPM doesn't really want anybody to use TAI, their director
said as much last year, and I can see where he is coming from on that

The snippy answer to why UTC was adopted for civil timekeeping would
be "Because they got bad advice", but that would be grossly unfair
since nobody (but possibly Dave Mills) at that time could be expected
to foresee what computer networks would result in and how that would
affect the needs for timekeeping.

Just like the variable rate atoms of the sixties where a bad idea
we now know that the variable length days that replaced them are

I'm not old enough to have any axe to grind about the last couple
of redefinitions of time, but I can see where they both went wrong
(insisting on using the unprecise and unstable clock to discipline
the stable and precise clock) and I want us to stop that mistake.

>Here we disagree. I guess you're confirming what is in fact the
>current problem as I see it. We're here because an ITU committee,
>shrouded in secrecy, is trying to redefine UTC and the international
>distribution of time signals, which most jurisdictions rely on one way
>or another as civil time.

But you overlook that ITU is an international organization under
the UN aegis.

If ITU in their plenary assembly decides to do something, no matter
how stupid, (X.400 for example), that is nontheless the will of
the governments of the world.

You can find locate your countrys ITU-R representative and contact
them with your input, just as well as I can for mine.

There is nothing hidden, undemocratic or revolutionary about it.
The ITU _process_ does actually work.

I will agree that a lot of what ITU churns out, UTC with leapseconds
and X.400 being my best examples, are rubbish.

>Some folks here suggest that legislatures just change their timezones
>periodically, forced by the actions of the ITU. But data was
>presented in Torino suggesting a cost to NASA and US DoD of a half a
>billion dollars to study, re-engineer and test their systems if UTC
>diverges markedly from UT1. Not an easy thing for a legislature to
>deal with. Again - it's a process problem....

Let me channel something that gets said a lot here:

    "They should have used the right timescale from the beginning".

It sounds like they should have used UT1, doesn't it ?

And why is it that IT related costs matter so much if they come from
people worried about the effect of lack of leapseconds, while at
the same time, they don't matter at all if they come from people
worried about the effect of leapseconds ?

Clearly what's good for the goose is good for the gander, right ?

>The only time there has been an inclulsive international meeting
>devoted to the issue, at the colloquium in Torino, "There was no
>overwhelming consensus on whether the status quo should be maintained
>or an alternative should be pursued."

... at that meeting.

The only consensus that matters is the ITU-R SG7A, which coincidentally
didn't reach one either.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk_at_FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Received on Sat Jan 07 2006 - 12:31:30 PST

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