[ntp:questions] Leap second functional question

Unruh unruh-spam at physics.ubc.ca
Mon Feb 18 23:35:46 UTC 2008

David Woolley <david at ex.djwhome.demon.co.uk.invalid> writes:

>Unruh wrote:
>> David Woolley <david at ex.djwhome.demon.co.uk.invalid> writes:
>>> Dean Weiten wrote:
>>>> As an example, let's say that there was a leap second to be added on 
>>>> 2008-02-10 at 23:59:59 (hmm, or is that 2008-02-11 at 00:00:00?).  This 

>> He is asking how it is added or subtracted. 
>> His date of Feb 11 was wrong, but was a trivial part of his question. He
>> wants to know HOW the second is added or subtracted. 

>The date error is significant because, once one realizes there are only 
>two possible days a year, it becomes unimportant when the flags are set 
>and cleared.  I have a suspicion that the transmission used not to be 
>limited to the date of change, so the code may not restrict their 
>forwarding because people were not limiting their implementation to 
>those particular days..

Well, no, it is still important on those days. It does not occur every year
or every day ( in fact I think we have not had one in about 4 years). 

>The current code basically checks the date and only sets the bits if it 
>is one of those two days.

No, it does not. It only sets the bit if it has been told by a majority of
its servers that a leap second is coming up. And we had a number of people
having trouble in that a leap second seemed to have been announced to them
in the middle of Jan this year. Ie, ntp on your system relies on your
servers to tell about leap second. It is announce a month before hand and
then on the day.

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