Leap Second Event Occurring on 30 June 2015

Number: IN15-001
Date: 26 June 2015


The purpose of this Information Note is to draw attention to the leap second that will be introduced on 30 June 2015 (00:00 UTC 1 July 2015) to align the UTC system with the rotation of the Earth. The leap second will necessitate an adjustment to all UTC clocks by one second.


The Coordinated Universal Time (UTC) time standard, based on atomic clocks, is widely used for international timekeeping and as the reference for time in most countries. UTC is the basis of legal time for most of the world. UTC must be adjusted at irregular intervals to maintain its correlation to mean solar time due to irregularities in the Earth's rotation. These adjustments, called leap seconds, are pre-determined. The next leap second will occur on 30 June 2015 at 23:59:59 UTC.

To implement the positive leap second, all UTC clocks will display an extra second. The date sequence of the UTC markers will be:

30 June 2015 23H 59M 59S
30 June 2015 23H 59M 60S (extra second)

Followed by: 01 July 2015 00H 00M 00S

Systems which receive UTC time corrections from external sources should be unaffected by the addition of a leap second. Systems that do not receive UTC time corrections from external sources may require manual resetting/synchronization of clocks.

Suggested action

CCIRC strongly encourages Industry and government Chief Information Officers to check and verify leap second insertion procedures on all systems dependent on precise time/UTC to verify leap second insertion will not disrupt normal operation. Please review the reference document for additional technical details.



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