Re: [LEAPSECS] The real problem with leap seconds

From: Clive D.W. Feather <clive_at_demon.net>
Date: Mon, 9 Jan 2006 10:01:27 +0000

Michael Sokolov said:
> http://ivan.Harhan.ORG/~msokolov/articles/leapsecs.txt
>
> The short summary is that I believe the root problem is not the
> adjustments made to the civil time scale to match Earth's rotation, but
> the fact that UTC is not expressible as a real number. Read the article
> for a detailed explanation of what I mean by that.

You've expressed it very badly in the article. The problem is not that UTC
can't be expressed as a real number. Rather (and you do sort of say this,
just not very well), the function UTC(TAI) is not continuous and monotonic.

Right now, the DTAI(TAI) function is the sum of a set of Kroneker delta
functions. It is thus monotonic but not continuous (though only
discontinuous in a few places). It is, of course, real.

> I encourage both pro- and anti-leap second advocates on this list to
> read my article since there is that slight possibility that the problem
> I point out (which I haven't seen anyone else point out so far)

It's one we've all been aware of for ages.

> and the
> solution I propose

which is Markus's UTS with trivial alterations

> my proposal would allow civil time to be well
> anchored to Earth's rotation without causing grief for computer systems
> like leap seconds currently do.

On the contrary, it would cause exactly the same grief. If your proposal
was a wonderful solution, then leap seconds would not be a problem either
because the two are trivially mappable (I'm assuming that there'd be a
"rubber second" flag).

The real problem is not the 23:59:60, it's *predicting* when they happen.

--
Clive D.W. Feather  | Work:  <clive_at_demon.net>   | Tel:    +44 20 8495 6138
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Thus plc            |                            |
Received on Mon Jan 09 2006 - 02:01:46 PST

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