A second chance for UTC
After more than a decade of consideration, on January 19 the Radiocommunication Assembly of the International Telecommunication Union (ITU-R) decided to postpone its decision on whether to redefine Coordinated Universal Time (UTC) for another three years. The fate of the so-called leap second—an occasional adjustment to keep atomic clocks in concordance with the heavens—therefore remains uncertain.
In a press release, the ITU-R said “the decision has been reached to ensure that all the technical options have been fully addressed in further studies related to the issue.” The Assembly’s decision parallels an earlier recommendation from an international meeting of concerned specialists that met at AGI in October. These professionals, having expertise in navigation, astrodynamics, astronomy, and other technologies, concurred that a decision to redefine UTC should be deferred because of a lack of evidence supporting the need for a change and insufficient exploration of the consequences thus far. A last-minute statement issued by an International Standards Organization (ISO) committee also affirmed that the proposal did not conform to other internationally established protocols, a point also discussed within the AGI meeting.
However, what will be gained by officially sending the proposal back to the originating study groups for three more years? At the study-group level, no agreement was found after exhaustive debate, which is why the study groups wanted the 2012 Radiocommunication Assembly to settle the controversy. The push to redefine UTC was fueled by claims that our synchronization of clocks and Earth rotation is dangerous, but the ITU-R’s lack of urgency signals that argument is not compelling to decision makers. The ITU-R’s indecisiveness also comes at a time when the former director of the International Bureau of Weights and Measures (BIPM) has argued that ITU-R oversight of the world’s civil time scale appears to be “an anomaly” and that others should take over. (Responsibility for UTC’s definition landed with the ITU-R because time signals were originally distributed by radio.)
While the ITU-R’s lack of action makes the long-term definition and ownership of UTC still uncertain, the definition of UTC since 1972 continues in force. So for those professionals who accurately use UTC past or present, support for leap seconds remains timeless.