freebsd-current Digest, Vol 127, Issue 4

Carlos Amengual listas at
Tue Jan 3 13:11:43 PST 2006

Poul-Henning Kamp wrote:
> The astronomers know far too little about modern computing.

Something shared with the POSIX specifications writers.

> The following proposals have been aired:
> A)  Abandon leap seconds.

See last paragraphs.

> B)  Predict leap seconds further in advance.
> 	This increases the |UT1-UTC| tolerance and the astronomers
> 	will have to cope.
> 	Provided that the notice becomes long enough, 10 years as
> 	a minimum, computing problems will mostly disappear, provided
> 	operating system suppliers pay attention to it.

Leap seconds cannot be predicted reliably. If you mean having an initial 
prediction and then issuing (supposedly less frequent) differential 
corrections, you still have the problem, but with more confusion added.

> C)  Make leapseconds smaller and more frequent

Then you loose the concept of a second and make the idea of timekeeping 
impractical. If I understand correctly, you agree with that and choose 
the idea of dropping the leap seconds:

> And finally some anti-FUD:
> [...]
> "We don't know what will break if we drop leap-seconds"
> 	We know very well what can break:  Only systems which relate
> 	the position of extra-terrestial objects to UTC time can break.
> 	These devices are called antennas and telescopes and they are
> 	operated by scientists and technicians who should be more than
> 	able to figure out how to deal with this.

You are missing the sextants, and their users, which would be much more 
complicated to "fix" than those telescopes. If leap seconds are dropped, 
ships and planes are going to notice it sooner or later.

You may think that all those users could be educated to use a new, 
modified procedure, but the fact that many people still talks about GMT, 
which was abandoned as a timescale years ago (together with the whole 
concept of "Mean Time"), should evidence that such a change is not that 

Carlos Amengual

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