[ntp:questions] Leap second functional question
unruh-spam at physics.ubc.ca
Tue Feb 19 16:44:42 UTC 2008
David Woolley <david at ex.djwhome.demon.co.uk.invalid> writes:
>> David Woolley <david at ex.djwhome.demon.co.uk.invalid> writes:
>>> 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
>> 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).
>But you can safely have it set for most of the previous six months and
>the following six months, whereas the questioner is assuming it must be
>cleared immediately the leap second has been implemented and not set
>more than a very short time in advance. (It certainly has to be set
>hours in advance, because some clients may not have polled within an
>hour, and each stratum can extend the propagation delay of the setting
>of the flags.)
>>> 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
You are right. I must admit I did not look at the code, but relied on my
obviously bad memory from a previous thread. Sorry.
... (code proving the bit is set only on June 30 or Dec 31 removed)
>> 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.
>That tends to confirm that it has been acceptable to set the flag any
>time after the preceding candidate time.
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