ITU continues debate on future of “leap second”

September 23, 2013 // By Graham Prophet
An ITU meeting in the last few days has returned to the subject of the feasibility of a continuous time scale, otherwise known as the debate on “To abolish or not abolish the ‘leap second’?”

Although apparently an arcane subject, this debate has implications for many electronic systems that use a variety of broadcast standards to maintain their timebases – not least, worldwide communications systems, and the operating systems in connected portable devices. And, familiar names in the test & measurement industry supply many of the clocks that act as references for those standards.

At issue is the future of UTC. To date, UTC has been periodically re-sychronised to the rotation of the Earth by adding “leap seconds”. This is essentially a random process as the Earth's rotation is unpredictably slowed by weather systems, tidal and geological forces. GPS time (to cite one contrasting standard) has counted continuously from a baseline and is not so corrected, and is therefore “out of step” with UTC. A proposal has been extensively debated that UTC should no longer be corrected; this would make it a continuous time standard but at the cost of having it slowly drift out of synchronisation with astronomical time. In 2012 the ITU decided, in effect, not to decide, and deferred making any changes; this past week has seen the latest step in the process, and the ITU's statement on the subject says;

“The future of the International Time Scale has been the subject of intense discussion this week at a workshop held jointly by ITU and the International Bureau of Weights and Measures (Bureau International des Poids et Mesures – BIPM). At the heart of the matter is the proposal to abolish the so-called ‘leap second’ to adjust to the earth’s rotation in relation to Coordinated Universal Time (UTC), the current standard for measuring time. The suppression of the leap second would make continuous time scale available for all the modern electronic navigation and computerised systems to operate with and eliminate the need for specialised ad hoc time systems.

“ITU membership along with other organizations has been studying the consequences of eliminating the