The leap second: its history and possible future


This paper reviews the theoretical motivation for the leap second in the context of the historical evolution of time measurement. The periodic insertion of a leap second step into the scale of Coordinated Universal Time (UTC) necessitates frequent changes in complex timekeeping systems and is currently the subject of discussion in working groups of various international scientiŽ c organizations. UTC is an atomic time scale that agrees in rate with International Atomic Time (TAI), but differs by an integral number of seconds, and is the basis of civil time. In contrast, Universal Time (UT1) is an astronomical time scale deŽ ned by the Earth’s rotation and is used in celestial navigation. UTC is presently maintained to within 0.9 s of UT1. As the needs of celestial navigation that depend on UT1 can now be met by satellite systems, such as the Global Positioning System (GPS), options for revising the deŽ nition of UTC and the possible role of leap seconds in the future are considered.

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@inproceedings{Nelson2002TheLS, title={The leap second: its history and possible future}, author={R. A. Nelson and Dennis D. McCarthy and S. Malys and Jonathan S. Levine and Bernard Guinot and Henry F. Fliegel and Ron L Beard and Tracy Bartholomew}, year={2002} }