[time-nuts] FW: Bulletin C number 30

Poul-Henning Kamp phk at phk.freebsd.dk
Tue Jul 5 02:29:44 EDT 2005


In message <20050704.212118.87245102.cfmd at bredband.net>, Magnus Danielson write
s:

>> And btw, it probably would not even be a leap-second for him, since
>> general relativity would take its toll.  I'm not sure my grasp of the
>> math is good enough to figure out how long his leap-second would be.
>> 
>> Instead, if we abandon leap-seconds, then we finally have a _truly_
>> universal timescale.
>> 
>> It will not be locked to any more or less random piece of geophysics,
>> anyone with a cesium clock and a set of gen-rel coordinates will be
>> able to figure out what time it is, and time intervals can be measured
>> and compared without weird gottchas.
>
>No. You are missing a detailed refinement in the definition of a second, it is
>assumed that the Cesium clock is at sea-level.

Sea-level on this planet, yes.

If you are on a different planet in a different orbit and a differnet
rotation period (and axis!), general relativity takes a toll.

If you bring a HP5071A to Mars, it will give you a wrong length of
seconds.

>Considering how time-zones is set, I start to wonder. Look at the time zones
>in South America and you see what I mean.

Just look at Europe :-)

>> The other half is that leap-seconds are just not testable in a computer
>> setting, and therefore I am sure that any cost of dropping them will
>> be totally offset by the savings in the IT industry.
>
>I am not even sure that the IT industry is really spending a whole lot on this
>issue. Most of them is to the best of my knowledge fairly ignorant to this
>among other problems. Just having charging systems track UTC through NTP would
>be a huge step forward IMHO.

Well, I think the disruption is obscured by the lack of implementation.
As more systems implement leapseconds (through NTP or otherwise) we will
see more applications which didn't do it quite right.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.




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