On Thu 2006/01/12 10:19:05 -0000, David Malone wrote

>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

Reply via email to