Session P1a: Transitioning to a New Definition of the SI Second

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Date: Tuesday, January 27, 2026
Time: 1:45 p.m. - 3:25 p.m.
Location: Royal Ballroom AB
In-Person presenters in this session provide pre-recorded presentations for viewing by registered attendees on Tuesday, January 28.

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In-Person Presentations These presentations will be given in-person at the conference. Presenters will provide a pre-recorded presentation for on-demand viewing by virtual attendees.
1:50	Towards the Redefinition of the Second   D. Calonico, INRIM; P. Tavella, BIPM; N. Dimarcq, ARTEMIS (Université Côte d’Azur, OCA, CNRS)
2:12	An Accessible Formulation for an SI Second Based on Multiple Atomic Transitions   Nils Nemitz, National Institute of Information and Communications Technology (NICT); Claudio E. Calosso, Istituto Nazionale di Ricerca Metrologica (INRiM)
2:35	Redefining the SI Second: A Simple Mathematical Insight into the Ensemble Option   C.E. Calosso, Istituto Nazionale di Ricerca Metrologica (INRIM); N. Nemitz, National Institute of Information and Communications Technology (NICT)
2:58	New Definition of the SI Second – Discussion Moderated by the Session Chairs
3:25 - 3:55, Break. Refreshments in Exhibit Hall

On-Demand Presentation Pre-recorded presentations will become available for viewing by registered attendees on Tuesday, January 28.
	Lessons from the 1967 Redefinition of the SI Second I. Mihailescu, Institute of History & Laboratoire Temps-Fréquence, Institute of Physics, University of Neuchâtel; C. Affolderbach, G. Mileti, Laboratoire Temps-Fréquence, Institute of Physics, University of Neuchâtel

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