Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Towards a consensus on a continuous Coordinated Universal Time



Judah Levine, Patrizia Tavella, Martin Milton


This paper discusses the considerations that were important in 1972, when the current leap second system was adopted, to maintain UTC, the international reference time scale, closely connected to UT1 – a time scale based on the rotation of the Earth. Although some of these considerations are still relevant, the method of adding leap seconds introduces difficulties with many modern applications, which depend on a continuous and monotonic time scale. We present the advantages and disadvantages of the leap second system, and some of the problems that will result if we do not make a change. We suggest the general outline of a way forward, which addresses the deficiencies in the current leap second system, and which will ensure that UTC remains an international standard that is useful and appropriate for all time and frequency applications. The details will be decided based on continuing discussions and evaluation of the impact of any changes.


Atomic time, GNSS time scales, Leap seconds, Time in digital systems, UTC


Levine, J. , Tavella, P. and Milton, M. (2022), Towards a consensus on a continuous Coordinated Universal Time, Metrologia, [online],, (Accessed June 25, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created November 25, 2022, Updated June 7, 2024