Re: [LEAPSECS] USNO leap seconds - a minmum-change approach

From: John Cowan <>
Date: Tue, 22 Aug 2000 14:10:17 -0400

Rob Seaman wrote:

> There is a very big difference between the random errors of the world's
> ensemble of clocks and a bias of 2+ minutes per century. Those couple
> of minutes are small for some uses, but immense for others.

It's a bias only on the assumption that "real" time is UT1 time, a reasonable
notion for an astronomer. But what if we think "real" time is TAI time?
Then the introduction of leap seconds is nothing but tampering with the
steady flow of time at 60 seconds per minute like God intended. :-)

> Whatever one's opinion of
> Apple Computer - an iMac is certainly a consumer item containing a clock.

Exactly what I'm getting at. There are now a large number of essentially
autonomous devices in this world that tick a very reasonable approximation
to TAI - some number of seconds. Their users, however, want to see something
different, mostly local civil time but sometimes UT1 time or some other
PTC (Peculiar Time Scale). There is no algorithmic way to convert TAI-offset
time to these other scales. If we are to spread the responsibility
of doing the conversion around, we introduce difficult-to-scale dependencies
on the primary IERS data.

> The MacOS date and time control panel includes ntp. Buy a Mac - buy a
> clock - and buy a clock that is designed to maintain good time with
> minimal effort.

In fact leap seconds are one of the primary uglifications of NTP; there is
no resolution if peers are Byzantine about whether today includes a leap
second or not.

Anyway, governments are marginal     || John Cowan <>
outside totalitarian states, though  ||
attention is always focused on them  ||
to direct it away from what matters. \\ -- Noam Chomsky (1995)
Received on Tue Aug 22 2000 - 11:20:57 PDT

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