A Brief History of UTC Leap Second


  • Włodzimierz Lewandowski National Institute of Telecommunications, Warsaw, Poland
  • Michał Marszalec National Institute of Telecommunications, Warsaw, Poland




atomic time, GNSS time scales, leap second, time in digital systems, UTC


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.


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Bureau International des Poids et Mesures (International Bureau of Weights and Measures), "Circular T", monthly report, [Online], Available: https://www.bipm.org/en/time-ftp/circular-t

International Earth Rotation and Reference Systems Service, "Bulletin C: Guide", [Online], Available: https://hpiers.obspm.fr/iers/bul/bulc/BULLETINC.GUIDE.html

CGPM, "Resolution 5. Coordinated Universal Time", 15th meeting of the General Conference on Weights and Measures (CGPM), 1975 https://www.bipm.org/en/committees/cg/cgpm/15-1975/resolution-5

International Telecommunication Union, "Recommendation ITU-R TF.460-6. Standard-Frequency and Time-Signal Emissions", in: ITU-R Recommendations: Time Signals and Frequency Standards Emissions, Geneva, 2002 https://www.itu.int/rec/R-REC-TF.460

R.A. Nelson et al., The Leap Second: its History and Possible Future, Metrologia, vol. 38, pp. 509-529, 2001. DOI: https://doi.org/10.1088/0026-1394/38/6/6

L. Essen and J.V.L. Parry, "An Atomic Standard of Frequency and Time Interval: A Cesium Resonator", Nature, vol. 176, pp. 280-282, 1955. DOI: https://doi.org/10.1038/176280a0

B. Guinot B and E.F. Arias, "Atomic Time Keeping from 1955 to the Present", Metrologia, vol. 42, no. 3, 2005. DOI: https://doi.org/10.1088/0026-1394/42/3/S04

Procedings-Verb. Comité International des Poids et Mesures, 1967, 35, 15; Metrologia, 1968, 4, 43; [41], 120.

Transactions of the International Astronomical Union, Vol. XIII B, Proc. 13th General Assembly, Prague, Czech Republic 1967 (Ed. L. Perek), 182.

CGPM, "Resolution 2. On the definition of time scales", in: 26th Meeting of the CGPM, 2018.

E.F. Arias and W. Lewandowski, "Role of International Time Reference UTC in the Definition of Galileo System Time", in: Symposium on Scientific and Fundamental Aspects of the Galileo Program, Toulouse, France, 2007.

E.F. Arias and W. Lewandowski, "GNSS Times and UTC", Metrologia, vol. 48, no. 4, 2011. DOI: https://doi.org/10.1088/0026-1394/48/4/E01

C. Han, Y. Yang, and Z. Cai, "BeiDou Navigation Satellite System and its Time Scales", Metrologia, vol. 48, no. 4, 2011. DOI: https://doi.org/10.1088/0026-1394/48/4/S13

J. Achkar and A. Bauch, "The Use of Galileo for Time Dissemination", in: Symposium on Scientific and Fundamental Aspects of the Galileo Program, Toulouse, France, 2007.

CCTF Recommendation S6 - 1999 - Future global navigation systems, approved by the 88th meeting of the Comité International des Poids et Mesures (CIPM) as Recomendation 1 CI-1999.

J. Levine, P. Tavella, and M. Milton, "Towards a Consensus on a Continuous Coordinated Universal Time", Metrologia, vol. 60, no. 1, 2023. DOI: https://doi.org/10.1088/1681-7575/ac9da5

ITU, "Proposed Addition to Working Document Towards a Preliminary Draft New Report ITU-R TF", in: ITU-R WP-7A (Polish Contribution 28), 2021.

Petition to ITU-R WP 7A of the International Timing and Sync Forum ITSF 2021, Brighton, 2021. [Online], Available: https://itsf2021.executiveindustryevents.com/Event/

CGPM, "Resolution 4. On the Use and Future Development of UTC", in: 27th Meeting of the CGPM, 2022 https://www.bipm.org/en/cgpm-2022/resolution-4

WRC, "Resolution 655. Definition of time scale and dissemination of time signals via radiocommunication systems", in: World Radiocommunication Conference (Revised version WRC-2023), Dubai, UAE, 2023.




How to Cite

Lewandowski, W., & Marszalec, M. (2023). A Brief History of UTC Leap Second. Journal of Telecommunications and Information Technology, 4(4), 117–122. https://doi.org/10.26636/jtit.2023.4.1486




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