News & Article


Notice on Leap Second

29 Dec 2016

Important Information on Leap Second Event Occurring

on 1 January 2017, 8.00am SST

 

We will experience a leap second in our civilian time on 1 Jan 2017 (Sunday) at 8.00am SST (Singapore Standard Time).

 

The leap second is applied whenever the difference between the solar time based on the Earth rotation and atomic time exceeds 0.9 second. The atomic time is the civilian time used by all countries, and it is called Coordinated Universal Time (UTC). The atomic time, which is based on quantum physics, is so accurate and consistent that the solar time cannot catch up due to the slowing down of the Earth rotation. Insertion of each UTC leap second is usually decided several months in advance by the International Earth Rotation and Reference Systems Service (IERS).

 

The world’s computer systems including the time servers are referenced to the UTC. Local realization of UTC is generally done by national time laboratory. As the custodian of the time standard in Singapore, NMC’s public standard time server will be sending a leap second flag in its time message to its users repeatedly before the insertion, to inform the user client software that a leap second is imminent. This allows the user client software to automatically adjust for the leap second.

 

During the actual leap second insertion interval, NMC’s server will be sending the time 23:59:59 for two times and then followed by 00:00:00. The users’ systems which already have updated firmware will be able to interpret the flag and handle the insertion process properly. However, if the systems’ firmware are still in an older version and have not been upgraded, they may not recognize the flag and do not have the capability to handle the insertion smoothly. As a result, these systems may show a wrong time.

 

To be better prepared for the coming leap second insertion, we strongly recommend our users to do the following:

  1. Check your system firmware version or contact your manufacturers for the latest update.
  2. Verify your Network Time Protocol (NTP) servers and client systems are built to account for leap second, and the insertion will not interrupt the system’s normal operation.
  3. Isolate the system from any external timing sources which may not work properly during the leap second insertion.
  4. An alternative way to mitigate the impact is to reduce or turn off the on-line application at that moment, to prevent possible system crash.

If you encounter incorrect time problem after the leap second insertion, you may reset the time or restart the system if necessary.

 

Should users require assistance on the leap second, they can contact us at 62791927 or 62791935, or email us at metrology@nmc.a-star.edu.sg during office hours.