[ntp:questions] A Suggestion For Abolishing the Leap Second

Martin Burnicki martin.burnicki at meinberg.de
Wed Jun 6 13:03:57 UTC 2007


Guy Macon <http://www.guymacon.com/> wrote:
> Martin Burnicki wrote:
>>I'm pretty sure Dave Mills is correct. For an introduction of leap seconds
>>and how they may be handled you migth have a look at
>>Search for "normalize" at the end of that section.
> I see that. Key phrase:
> "2 consequent seconds have the same time stamp"

Isn't that true for counting seconds?

2005-12-31 23.59.60 <-- leap second
2006-01-01 00.00.00

We can normalize the time and date of the leap second:
60 seconds are 1 minute, which lets the minutes increment from 59 to 60
60 minutes are 1 hour, which lets the hours increment from 23 to 24
24 hours are 1 day, which lets the date increment, and so on.

Finally we can say that both lines represent exactly the same time, or 2
consequent seconds have the same time stamp.

> A post in the comp.protocols.time.ntp mailing list goes into
> further detail:
> "every time a leap second happens, the fraction part
> of the  second, in the NTP timestamp keeps counting. That's
> the fraction part only. It does not roll over to the next
> second. Instead, the same second is repeated - thus we repeat
> the same time, which means we go back in time. However, the
> NTP timestamp sends out a leap second flag, which causes
> your computer to go to the 61st second."
> http://mailgate.dada.net/comp/comp.protocols.time.ntp/msg08459.html
> It looks like we were both wrong.  The NTP clock doesn't stop, as
> David L. Mills wrote, nor does it continue into a 61st second,
> which is what I thought it does.  Instead it jumps back a second
> and repeats the 60th second with a leap second flag set.

No, at least I'm not wrong. Did you also have a look at the rest of the page
I've mentioned? 

You must distinguish between how a leap second is defined in civil time, and
how it is handled by different implementations like operating systems, or
NTP. See the chapter "Operating Systems":

Did you also have a look at Dave Mills' reply to that news article you've
quoted above, and the link Dave has posted?

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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