[ntp:questions] Leap second to be introduced in June

schmidt.rich at gmail.com schmidt.rich at gmail.com
Fri Jan 23 19:03:23 UTC 2015


On Friday, January 23, 2015 at 3:55:02 AM UTC-5, Marco Marongiu wrote:
> On 21/01/15 15:31, Mike S wrote:
> > On 1/21/2015 2:10 AM, Mike Cook wrote:
> >> And one of the reasons why a significant portion of the computing
> >> community wants to get rid of leap seconds. A coverup for bad
> >> engineering practices.
> > 
> > That's right. Instead of recognizing that the world rotates on it's own,
> > they want to change reality so the world rotates around them. Lazy ass
> > programmers, trying to claim that leap seconds cause issues, when it is
> > software which doesn't handle time properly which is the root cause.
> 
> Two days ago I've been interviewed by the Italian national radio
> broadcaster about the leap second. It was between 11:30-12:00 Rome time.
> 
> Closing the interview the host asked me "I guess you would be happy if
> the leap second was suppressed, you'd have quite less problems to
> handle, wouldn't you?!". And I replied "I'd actually be happier if
> programmers did their job properly, for example not assuming that a
> minute always lasts 60 seconds, no matter what".
> 
> Funny that 3 hours later, on the other side of the planet, you have
> written the same thing...
> 
> It's a +1 from me, too. I guess it was clear ;-)
> 
> Ciao
> -- bronto

That was a cute response, but entirely misses the point of the problem with leap seconds. One can program in a leap second only if one knows it is coming. (Though I cannot program the leap second into my vintage 1855 Bond marine chronometer!)  What shall you program about the end of June, 2016, or December, 2020?  What will be the interval of time between now and then?  If you imagine the Earth is a UTC clock, and a transit telescope pointing to the Sun represents the hour hand, we would like to be pointing at the Sun again 24 hrs later.  But because the Earth is (now) a poor clock, sometimes it makes it all the way around in a day, and  sometimes it does not. In 2015, the Earth is taking per day on average 1.0092 milliseconds more than 24 hours to make a complete rotation.  And keep in mind that the estimated accuracy of the value of TAI-UTC 30 days out is three times that daily value, or 3.2 ms.  That's the best we can do at present.  

By eliminating the artifice of leap seconds we no longer need historical tables to compute for example the interval of time between two points moving forward. Astronomers are there already in the use of TT (Terestrial Time) in the computation of ephemerides, which avoids the discontinuity of leap seconds.  [Future inhabitants of Mars will have a completely different determination of "leap seconds"]. 

The US will soon be considering a means for dissemination of delta T via NTP, which further paves the way for practical elimination of leap seconds.  The ITU has just met in Geneva and discussed the future of leap seconds. The US is in favor of dropping them, the Brits are in favor of keeping the tradition of leap seconds, and the Swiss, who found support for both sides, has declared itself "neutral" (of course!)



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