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Introduction of a Leap Second

The Ministry of Internal Affairs and Communications has announced the introduction of a leap second at 1st January, 2017. (Details are below link)
http://www.soumu.go.jp/menu_news/s-news/01tsushin03_02000177.html (Japanese Only)

As a result of a leap second, servers or network equipment may be affected by the leap second. Please refer the following guide to prepare and prevent any problems or downtime.

Leap second implementation status of Operating Systems

Leap second implementation status of common operating systems are listed below. However, please contact the vendor for further information.


Leap second processing is not handled by the Windows operating systems. No special instructions are needed for the Windows systems.
A time difference of about one second occurs after the leap second. However, the time synchronization service will correct the local clocks when it synchronizes the time from its upstream NTP servers.

See Also: https://support.microsoft.com/en-us/kb/2722715


For Linux systems, some issues such as high CPU load, are reported at last leap second introduction. Please keep your system up-to-date.
However, if the applications or daemons don't support the leap second, please follow the steps below to prevent the potential issues.

  1. Stop NTPd (time synchronization daemon) before 9:00 1 January 2017(UTC+9) to delete the leap indicator.
    (Note: No leap indicator will be delivered to NTPd daemon if the daemon has stopped before 9:00 31 December 2016(UTC+9))
    See Also: https://access.redhat.com/articles/199563
  2. Start NTPd daemon after leap second introduction.

Leap second may cause kernel panic for old version kernels. Most conservative workaround is stopping the system before 9:00 1 January 2017(UTC+9). Please refer the following link if the system is mission critical.

See Also: https://access.redhat.com/solutions/2441291

macOS (OS X)

Leap second processing is not handled by the macOS operating systems. No special instructions are needed for the macOS systems.

Leap second support status of internal NTP servers at Keio University

NTP servers operated by ITC will set a leap indicator as "01" after 9:00 31 December 2016 (UTC+9) to notice the introduction of leap second. If the system is capable to leap indicator, the system will process the leap second at 9:00 1 January 2017 (UTC+9).

Leap indicator will be cleared to "00" as a normal status on 9:00 1 January 2017 (UTC+9).

Last-Modified: December 20, 2016

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