Re: [LEAPSECS] Defining our terms (was Re: [LEAPSECS] Longer leap second notice)

From: Poul-Henning Kamp <>
Date: Sat, 07 Jan 2006 09:13:52 +0100

In message <>, Steve Allen writes:
>On Sat 2006-01-07T00:32:44 +0100, Poul-Henning Kamp hath writ:

>> UTC
>> UTC(time) = TAI(time) + Leap(time)
>> Owned by ITU.
>> IERS evaluates Leap(time) according ITU definition
>Not quite. The endorsement for the usage of UTC comes from CGPM,
>and that is predicated on the existence of leap seconds.

This is irrelevant.

The CGPM may endorse which timescale they think should go into legal
time, but if they change their mind UTC will still exist until ITU
does something about that.

A secondary issue is that even if CGPM decided to say "Use FOO instead"
nobody would take much notice until ITU and a lot of other people
agreed and did their respective paperwork.

>But in the original agreement, UTC and TAI were defined solely by the
>BIH according to the rules of the CCIR. Both the BIH and the CCIR are
>defunct. TAI was transferred from BIH to the BIPM. Determination of
>the UTC offset was transferred from BIH to IERS. But IERS is not
>a single entity, it is an ensemble of entities.

Lets waste a lot of time splitting red tape, why don't we ?

>At the beginning of 1984 and at the beginning of 2003 the branches of
>the IERS responsible for UT1 followed new IAU recommendations and
>changed the rules by which UT1 is calculated. The current version
>of UT1 has a notably different flavor and long-term purpose than
>the version of UT1 which was in place when UTC with leap seconds
>was originally defined by the CCIR.

But that matter, because ITU-R (successor of CCIR) defined Leap(time)
in terms of UT1 without specifying how UT1 was arrived at.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Received on Sat Jan 07 2006 - 00:24:07 PST

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