Some of you may not have noticed this in the post-Christmas doze …
What will happen is that on 30th June [UTC time] the clock will go 23:59:59 > 23:59:60 > 00:00:00, instead of 23:59:59 > 00:00:00, i.e. an extra ‘leap’ second is inserted.
It will cause the odd issue or two, depending on your environment and operating system..
For example, if you should happen to use RHEL you could start here https://access.redhat.com/articles/15145
There were certainly issues in other Linux distributions (including Oracle Linux and SLES) last time this happened on 30th June / 1st July 2012.
This year will be slightly longer after the Paris Observatory announced that it was adding a "leap second" at midnight [UTC] on June 30
Note: Midnight [UTC] on June 30 2015 is Noon, Wednesday, 1 July 2015 NZ Standard Time
INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS)
SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE SERVICE DE LA ROTATION TERRESTRE DE L'IERS OBSERVATOIRE DE PARIS
61, Av. de l'Observatoire 75014 PARIS (France)
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Paris, 5 January 2015 Bulletin C 49
To authorities responsible for the measurement and distribution of time UTC
TIME STEP on the 1st of July 2015
A positive leap second will be introduced at the end of June 2015. The sequence of dates of the UTC second markers will be: 2015 June 30, 23h 59m 59s 2015 June 30, 23h 59m 60s 2015 July 1, 0h 0m 0s
The difference between UTC and the International Atomic Time TAI is: from 2012 July 1, 0h UTC, to 2015 July 1 0h UTC : UTC-TAI = - 35s from 2015 July 1, 0h UTC, until further notice : UTC-TAI = - 36s
Leap seconds can be introduced in UTC at the end of the months of December or June, depending on the evolution of UT1-TAI.
Bulletin C is mailed every six months, either to announce a time step in UTC or to confirm that there will be no time step at the next possible date.
Earth Orientation Center of IERS Observatoire de Paris, France