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Establishment of a CCTF Task Group to address progress towards a continuous UTC

The 27th meeting of the CGPM (2022) adopted Resolution 4 On the use and further development of UTC. Subsequently, the CCTF Working Group on Strategic Planning established a task group (TG) in May 2023 to address the progress towards a continuous UTC.

The TG shall work together with the CCTF, laboratories that contribute to UTC, GNSS providers, International Organizations - such as the International Astronomical Union, the International Telecommunication Union (ITU), the International Earth Rotation and Reference Systems Service (IERS) - and other stakeholders to prepare a draft resolution for the 28th meeting of the CGPM (2026) including:

  • the extended tolerance value of UT1-UTC*
  • the procedure to align UTC to UT1 when the new tolerance is reached
  • the revision periodicity of this decision by the CGPM
  • the exact implementation date.

The TG aims to provide support to ITU delegations so that they are well prepared for the 2023 ITU World Radiocommunication Conference, where the update on UTC will be considered. Finally, the TG will foster communication efforts to increase awareness about this initiative, which will have profound implications for the future of reference time scales. Educational materials and promotional initiatives will be developed and shared over the coming years.

The TG looks forward to submitting a proposal to the 28th meeting of the CGPM that takes into account the requests and constraints of the different communities, while enabling UTC to be universally accepted, robust and useful.

* UTC - Coordinated Universal Time - is a time scale produced by the International Bureau of Weights and Measures (BIPM) with the same rate as International Atomic Time (TAI). It differs from TAI only by an integral number of seconds.

   UT1 is the time scale describing the angular rotation of the Earth.

The offset between the Earth rotation (UT1) and the Coordinated Universal Time (UTC) over the past 10 years. When this quantity approaches 0.6 s, a leap second is inserted (vertical line). The previous leap second was applied in 2016. In the last three years the Earth has stopped decelerating and has started rotating faster. If this trend continues for the next 10 years, the need would arise to remove one second, instead of adding one. This has never been the case before and has never been tested. It is of concern due to potential system failures that could be caused by an incorrect application.