UTC Leap Second Announced for June
January 10, 2012News courtesy of CANSPACE Listserv.
The International Earth Rotation and Reference Systems Service (IERS) has announced that a positive leap second will be introduced into Coordinated Universal Time (UTC) at the end of June 2012.
UTC will be retarded by 1.0 second so that the sequence of dates of the UTC markers will be:
2012 June 30 23h 59m 59s
2012 June 30 23h 59m 60s
2012 July 01 0h 0m 0s
UTC and all time scales based on UTC will be affected by this adjustment. However, GPS will not be adjusted physically. For GPS, the leap second correction contained within the UTC data of subframe 4, page 18 of the navigation message transmitted by satellites will change.
Before the leap second:
GPS-UTC = +15s (that is, GPS is ahead of UTC by fifteen seconds)
After the leap second:
GPS-UTC = +16s (GPS will be ahead by sixteen seconds)
While a leap second can be added at the end of any month, preference is given to the end of December and June, with second preference given to the end of March and September. Only December and June dates have been used so far.
Meanwhile, at the International Telecommunication Union's Radiocommunication Assembly 2012 meeting, immediately preceding the World Radiocommunication Conference 2012 (WRC-12), in Geneva later this month, a revision of Recommendation ITU-R TF.460-6 "Standard-frequency and time-signal emissions" will be voted on. The proposed revision eliminates the use of leap seconds in the UTC time scale on approximately January 1, 2018 (five years after the bringing into force of the Final Acts of WRC-12, should WRC-12 elect to incorporate the revised Recommendation into the Radio Regulations).
One of the first public documents suggesting the elimination of leap seconds was the article "GPS and Leap Seconds: Time to Change?", which appeared in GPS World magazine in November 1999.
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