[ntp:questions] Lep seconds

Unruh unruh-spam at physics.ubc.ca
Fri Jan 4 18:25:27 UTC 2008


Martin Burnicki <martin.burnicki at meinberg.de> writes:

>Mark,

>Mark Newman wrote:
>> Unruh - thanks for responding.  You are the only one
>> who did.
>> 
>> I certainly did not mean to disparage NTP time.  I
>> have spec'ed that it be used on our system.  Where I
>> run into problems is when a leap second occurs.
>> According to everything I've read when  NTP signals
>> the operating system that the second is occurring it
>> also outputs time.  It uses the POSIX standard method
>> - duplicate a second (or in some cases stretch the
>> last second).  This causes confusion when a time
>> sample is taken before the leap second and one during
>> the leap second.  The UTC standard (which only
>> addresses ascii time representations) actually counts
>> the second 0..60 rather than 0..59.

>If you "normalize" the time with second 60 then you see there _is_ a
>duplicate time stamp. This is because a leap second _is_ a inconsistency of
>time.

No there is not. Just like a leap year is not an inconsistancy of time. 
It is not inconsistant to add a leap second. It may be a pain for some
purposes (eg if you are an astronomer), but then so areleap years, and I
do not hear for a great push that we go onto say lunar time, for which each
year is exactly the same.

> 
>> At this point I am obligated to use UTC and NTP.

>On most Unix-like kernels NTP just passes a leap second announcement to the
>OS kernel, and the kernel handles the leap second in the way it is
>implemented in the kernel. For details, please see
>http://www.meinberg.de/english/info/leap-second.htm




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