Three time resolutions at the 2026 CGPM
Key facts
- The 28th CGPM is scheduled for 13–15 October 2026 at the Palais des Congrès de Versailles. [1]Official
- The convocation of 13 January 2026 lists six draft resolutions, lettered A to F, plus a draft on the dotation of the BIPM. [2]Official
- Three of the six drafts concern time: B on the definition of the second, C on the continuity of UTC, and D on a lunar reference time scale. [2]Official
- Lunar time is item 17 of the provisional agenda, and the votes on all resolutions are item 25. [2]Official
- No vote has been taken. The conference has not met, and the CIPM records two decisions on the lunar draft so far. [3]Official
The General Conference on Weights and Measures is the diplomatic body of the Metre Convention. Its 28th meeting is scheduled for 13–15 October 2026 at the Palais des Congrès de Versailles [1]Official. Six draft resolutions have been circulated to member states ahead of it [2]Official.
Three of the six are about time. That is unusual, and it is the reason lunar time reaches this particular meeting rather than a later one.
Why three of the six drafts are about time
The three time drafts are not variations on one question. They sit at three different levels of the same system.
Draft Resolution B concerns the unit itself. Draft Resolution C concerns the scale that the world reads, Coordinated Universal Time. Draft Resolution D concerns a second scale, for a second body, tied back to the first [2]Official.
A change at any one level constrains the others. That is why the same conference is asked all three questions in the same week.
The three time drafts side by side
The titles below are quoted from the convocation of 13 January 2026, which is the document sent to member states [2]Official. The third column is our summary of the subject matter, not a quotation from the draft texts.
| Draft | Subject, verbatim from the convocation | What it would change | Source |
|---|---|---|---|
| B |
|
The definition of the SI second, the base unit every other time scale is built on | [2]Official |
| C |
|
The technical arrangements that keep UTC running as one continuous scale | [2]Official |
| D |
|
Whether a lunar reference time scale is defined at all, and how it is tied to UTC | [2]Official |
The other three drafts of the six are not about time. They cover adherence to the Metre Convention, the digital transformation of metrology, and rules of procedure for the conference itself [2]Official. A seventh draft, lettered V, covers the dotation of the BIPM for 2028 to 2031 [2]Official.
Where the three sit on the agenda
The provisional agenda takes the drafts in order. Draft Resolution B is item 15, C is item 16 and D is item 17 [2]Official. Delegates may put their own proposals at item 24, and the votes on all resolutions come after that, at item 25 [2]Official.
The order of business is set out in how the CGPM votes on a draft resolution. The text of the lunar draft, and the committee decisions behind it, are covered in what Draft Resolution D proposes.
What the lettering does not tell you
The letters are not a ranking. They are the order in which the drafts appear in Annex 1 of the convocation [2]Official.
The letters have also moved. The CIPM outcomes page uses an earlier, committee stage lettering in which the digital transformation draft is B and the redefinition of the second is E [3]Official. This site follows the convocation, because that is the document member states received. The full document page for Draft Resolution D sets both letterings out side by side.
What is not on this agenda
None of the three drafts creates a running time scale. Draft Resolution D asks for a definition and for traceability to UTC; it does not name an organization to compute the scale or a date to start [2]Official. The IAU had already asked international organizations to agree those relations in 2024 [4]Official, and the CCTF has been holding workshops with space agencies and lunar system providers in the run-up to the conference [5]Official.
National deadlines run on their own clock. A United States memorandum of 2 April 2024 asks NASA for a finalized implementation strategy no later than 31 December 2026, whatever happens at Versailles [6]Official. Both outcomes are set out in what happens after the vote.
More of our coverage of the conference is collected in the lunar time news hub, and the wider chain of decisions is on the timeline.
Sources
- 28th meeting of the CGPM (2026)
- Convocation of the 28th meeting of the CGPM (O/Ref AK-CFA-2026-1001)
- Meetings of the CIPM: Outcomes
- Resolution on the establishment of a coordinated lunar time standard by international agreement
- Latest Updates from 2025 CCTF Meeting
- Policy on Celestial Time Standardization
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