[time-nuts] Fwd from NANOG: Erroneous Leap Second Introduced at2014-06-30 23:59:59 UTC

David J Taylor david-taylor at blueyonder.co.uk
Tue Jul 1 02:36:32 EDT 2014

Begin forwarded message:

> From: Tim Heckman <t at heckman.io>
> Date: June 30, 2014 at 17:33:52 PDT
> To: nanog at nanog.org
> Subject: Erroneous Leap Second Introduced at 2014-06-30 23:59:59 UTC
> Hey Everyone,
> I just was alerted to one of the systems I managed having a time skew
> greater than 100ms from NTP sources. Upon further investigation it
> seemed that the time was off by almost exactly 1 second.
> Looking back over our NTP monitoring, it would appear that this system
> had a large time adjust at approximately 00:00 UTC:
> - http://puu.sh/9Rs6O/a514ad7c97.png (times are in Pacific in these
> graphs, sorry about that)
> A few of our systems did alert early this morning, indicating they
> were going to be receiving a leap second today. However, I was unable
> to determine the exact cause for NTP believing a leap second should be
> added. And after some time a few of the systems were no longer
> indicating that a leap second would be introduced.
> This specific system is hosted in AWS US-WEST-2C and uses the
> 0.amazon.pool.ntp.org pool.
> Has anyone else seen any erroneous leap seconds being added to their 
> system?
> Cheers!
> -Tim Heckman

The systems here all appear OK, but I am running the latest development NTP 
which has more protection against a leap-second being flagged by a single 

SatSignal Software - Quality software written to your requirements
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Email: david-taylor at blueyonder.co.uk 

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