Re: [LEAPSECS] the legacy of ephemeris time

From: Poul-Henning Kamp <>
Date: Sun, 07 Dec 2003 10:26:51 +0100

In message <>, Steve Allen writes:

>For the sake of air traffic controllers, however, I wonder if the
>solution is not to demand the use of a uniform time scale and to
>enforce a lack of confusing by expressing that in a notation that is
>suitable for a uniform time scale. I.e., rather than use the
>inappropriate (and confusing) hh:mm:ss notation, why not require that
>the uniform time scale be reported as 5 significant digits of decimal
>fraction days or the 4 least significant decimal digits of a count of

It's not often that I can contribute to this subject, but for this
one I happen to be able to:

I have recently had professional reason to learn about timekeeping
in airtrafic control systems in Europe and the main operational use
of time is for communicating with pilots. Typically information
about when they expect to be where, how much they are delayed etc.
The secondary operational use of time is for worktime-regulations.

So to go to decimal time (again, didn't the french try this during
the revolution of Paris ?) you would have not only traffic controllers
and their computers, but also a major slice of the airline industry
to convert.

As long as leap-seconds only result in "a few seconds of glitches",
they don't care much about it, the system is designed to cope with
glitches and the staff trained for it, so as long as it gets back
on track fast, they don't worry too much about it.

Still, they'd be happier if they didn't have to cope with leapseconds.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Never attribute to malice what can adequately be explained by incompetence.
Received on Sun Dec 07 2003 - 01:37:10 PST

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