Re: [LEAPSECS] Time after Time

From: Poul-Henning Kamp <>
Date: Mon, 24 Jan 2005 10:32:37 +0100

In message <>, Markus Kuhn writes:

>In summary: There are basically three proposals on the table:
> a) Keep UTC as it is (|UTC - UT1| < 900 ms) and just make TAI more
> widely available in time signal broadcasts
> b) Move from frequent UTC leap seconds to far less frequent UTC leap
> hours, by relaxing the UTC-UT1 tolerance (e.g., |UTC - UT1| < 59 min)
> c) Remove any future leap from UTC, such that UTC becomes TAI plus a fixed
> constant (i.e., |UTC - UT1| becomes unbounded and will start to grow
> quadratically). In this scenario, LCTs would have to change their
> UTC offset every few hundred years, to avoid day becoming night
> in LCTs.
>My views:
> a) is perfectly fine (perhaps not ideal, but certainly workable)

This is where we disagree: leapseconds are too small and too
infrequent (in the next century at least) to be taken sufficiently
serious in computer programming. The community which benefit from
sticking with a) is so small and so far more capable of dealing
with the complexity than the rest of the planets sentient population.

> b) is utterly unrealistic and therefore simply a dishonest proposal
> (UTC is so popular today in computing primarily because it is
> *free* of leap hours)

Well, it is not unrealistic, in fact it may be the only realistic
way to implement c) as it allows the ITU-T delegation to vote for
the proposal without exceeding their mandate and gives us a couple
hundred years to allows the countries time to adapt their legislation
before we admit that c) was what we wanted all along.

> c) I could live with that one, but what worries me is that
> it will create a long-term mess in a few millenia, when
> |UTC-LCT| >> 1 day.

You know, amongst the things we have to worry about in the next
couple of millenia, this is waaaaay down the list.

If it comes to that, we don't even know what melting the icecap on
Greenland or having a new ice-age (take your pick :-) will do to
the earths rotation rate, and both are events which have (p > .1)
over the next 2500 years.

And I am sure that the simple farmer society living in pact with
mother nature avoiding all technology or the colonies around distant
stars (take your pick) will find it most amusing that they have to
fiddle with their timescale because the old home planet had a bunch
of boffins decide that for them 2000 years ago.

> I am annoyed that this long-term mess and solutions
> around it are not even being discussed.

Very few people have a horizon that long, and since this is all
conventional anyway, most realize that conventions live only a
few generations after the brains who wrote them.


If we call the rotational time of Earth "universal", what are we
going to call the rotational time of Mars ?

Certainly I would not expect an "universal time" to be adjusted
because of the variability of rotation of one specific planet.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Received on Mon Jan 24 2005 - 01:42:51 PST

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