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Lunar time news ahead of the 28th CGPM

Five articles on the decisions scheduled for October 2026: what is on the agenda, what the lunar draft says, how the conference votes, what the leap second draft proposes, and what follows either way.

Key facts

  • The 28th CGPM is scheduled for 13–15 October 2026 at the Palais des Congrès de Versailles. [1]Official
  • Lunar time reaches it as Draft Resolution D, item 17 on the provisional agenda circulated on 13 January 2026. [2]Official
  • Three of the six draft resolutions concern time: the definition of the second, the continuity of UTC, and a lunar reference time scale. [2]Official
  • No vote has been taken. Every article in this hub was written before the conference met. [3]Official

The decision ahead

The next dated decision on lunar time is a vote at the 28th General Conference on Weights and Measures, scheduled for 13–15 October 2026 in Versailles [1]Official. Everything in this hub was written before that conference met, and every sentence about the outcome is conditional for that reason.

The text and the procedure

Two questions come up more than any others: what the lunar draft actually says, and who decides it. The first is answered from the convocation and the CIPM record [3]Official; the second from the provisional agenda of the meeting itself [2]Official.

The leap second item

Lunar time is not the only time question at this conference. Draft Resolution C, item 16 of the provisional agenda, proposes 20 May 2027 as the implementation date for the larger limit on UT1 minus UTC that the 27th CGPM decided on in 2022 [3]Official. It reaches the same session as the lunar draft, and for the same reason: both are about what UTC is tied to [2]Official.

Both outcomes

The outcome is not known, so we do not write as if it were. The last article sets out what a carried draft would change, what a rejected one would leave in place, and which deadlines hold either way — including the United States date of 31 December 2026, which is national policy rather than a conference decision [4]Official.

Everything in this hub

All five articles, each with the first of its key facts. The primary text itself is on the document page forDraft Resolution D, the status of every organisation is on the tracker, and the chain of decisions that leads here is onthe timeline. This hub has its ownRSS feed. Writing about the vote yourself? Thepress kit collects the quotable figures, their sources and the diagrams as files.

  1. Three time resolutions at the 2026 CGPM

    Six draft resolutions reach the 28th CGPM in October 2026. Three of them are about time: the second, the continuity of UTC, and a lunar time scale.

    The 28th CGPM is scheduled for 13–15 October 2026 at the Palais des Congrès de Versailles. [1]Official

  2. What CGPM Draft Resolution D proposes

    Draft Resolution D asks the 28th CGPM to define an international lunar reference time scale traceable to UTC. What it covers, and what it leaves open.

    Draft Resolution D covers the definition of an international lunar reference time scale and its traceability to UTC. [2]Official

  3. How the CGPM votes on a draft resolution

    Who sits in the room at the 28th CGPM, how a draft resolution reaches a vote, where lunar time falls in the order of business, and what a vote settles.

    The convocation of 13 January 2026 was addressed to the embassies in Paris of the States Parties to the Metre Convention. [2]Official

  4. What happens after the votes at the 28th CGPM

    The 28th CGPM can carry Draft Resolutions C and D or leave them aside. Both outcomes for each, and the deadlines that hold whichever way the votes go.

    The conference has not met. Draft Resolutions C and D can each be carried, amended on the floor, or left aside. [2]Official

  5. Leap seconds and the October 2026 vote

    Draft Resolution C proposes 20 May 2027 as the implementation date for a larger UT1 minus UTC limit. What is decided, what is proposed, what stays open.

    Resolution 4 of the 27th CGPM, in 2022, decides that the maximum value for the difference UT1 minus UTC will be increased in, or before, 2035. [5]Official

Sources

  1. 28th meeting of the CGPM (2026) — Bureau International des Poids et Mesures, . Official document. Verified .
  2. Convocation of the 28th meeting of the CGPM (O/Ref AK-CFA-2026-1001) — Bureau International des Poids et Mesures / CIPM, . Official document. Verified .
  3. Meetings of the CIPM: Outcomes — Bureau International des Poids et Mesures, . Official document. Verified .
  4. Policy on Celestial Time Standardization — White House Office of Science and Technology Policy, . Official document. Verified .
  5. Resolution 4 of the 27th CGPM (2022): On the use and future development of UTC — Bureau International des Poids et Mesures — 27th General Conference on Weights and Measures, . Official document. Verified .
  6. Latest Updates from 2025 CCTF Meeting — Bureau International des Poids et Mesures, . Official document. Verified .
  7. Resolution on the establishment of a coordinated lunar time standard by international agreement — International Astronomical Union, Commission A3 — XXXII General Assembly, . Official document. Verified .

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