The leap second debate

Abstract

Coordinated Universal Time (UTC) is the standard civil time scale available via time signals in use in most parts of the world today. Leap seconds are the means to keep civil time, or UTC, aligned with adjusted Universal Time (UT1), a time based on Earth rotation corrected for polar variation. They are intentional adjustments to UTC that are instituted to prevent the difference between UT1 and UTC from exceeding +/- 0.9 seconds, based upon international agreement. Over a decade ago various technical communities for whom a continuous time scale would be more suitable than UTC, as disseminated in real-time, currently provides began making a case that the definition of UTC should be changed to eliminate leap seconds as a way to specify time unambiguously. This issue was discussed at the 2012 World Radiocommunications Conference (WRC), but consensus for elimination of the leap second was not achieved and a decision was postponed until the 2015 WRC.

This report examines the leap second debate by summarizing general concepts of time and basic aspects of the leap second, followed by a discussion of non-technical considerations, technical aspects, and possible solutions.