A Brief History of UTC Leap Second

Abstract

Since 1972, a leap second has been added, approximately once a year, into UTC, the world's atomic time scale used for civilian purposes, to keep it in phase with the Earth's rotation. Leap seconds ensure that the Sun remains over the Greenwich meridian at noon, with the accuracy of approximately 1 s. The issue of adding the leap second has been debated since 2000 by different working groups of various international organizations, especially ITU-R WP 7A. The main question remains whether the need for the leap second still exists, as its introduction is associated with numerous technical inconveniences. An overwhelming opinion that prevails in those groups is that it would be more beneficial to let the atomic time run its course and accept that the world's civilian time scale is bound to slowly diverge from the rotation of the Earth. The National Institute of Telecommunications has become, in recent years, one of the leaders of this process. This article provides a brief history of the current UTC-related practices and outlines various potential solutions to the problem.