Re: [LEAPSECS] The real problem with leap seconds

From: Mark Calabretta <mcalabre_at_ATNF.CSIRO.AU>
Date: Fri, 13 Jan 2006 12:32:27 +1100

On Thu 2006/01/12 10:19:05 -0000, David Malone wrote
in a message to: LEAPSECS_at_ROM.USNO.NAVY.MIL

>The reason that I came to this conclusion is because none of the
>documents I've read say that UTC can be expressed as a real number
>- they all suggest it is expressed as labelled seconds. (For example,
>see the way that Rec. 460-4 gives UTC values - I've never seen an
>official looking document that tries to write UTC as a real.)

I have two time scales, TAI and UT1, that tick at very slightly
different rates. I want to make TAI the basis for civil time keeping
but I need to make adjustments occasionally to keep it in step with
UT1. How do I do it?

The answer provided by CCIR was to represent TAI in a variable-radix
notation that matches (or appears to match), to within 0.9s, that of
UT1 expressed in the usual calendar/clock format. This is done by
varying the radix of the seconds field in a pseudo-sexagesimal clock
format from 60 to 61 (or in principle 59) on occasions announced 6
months in advance.

So if asked for a definition I would say that "UTC (post 1972) is a
representation of TAI such that ... (you know the rest)".

The point is that UTC is simply a representation of TAI. "Writing UTC
as a real" reveals it to be TAI.

Mark Calabretta
Received on Thu Jan 12 2006 - 17:32:56 PST

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