Resolution 9 of the 11th CGPM (1960)

Definition of the unit of time (second)

The 11th Conférence Générale des Poids et Mesures (CGPM),


  • the powers given to the Comité International des Poids et Mesures (CIPM) by the 10th CGPM to define the fundamental unit of time,
  • the decision taken by the CIPM in 1956,

ratifies the following definition:

"The second is the fraction 1/31 556 925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time."

DOI : 10.59161/CGPM1960RES9E

The reader should note that the official version of this Resolution is the French text


This definition was abrogated in 1967 by the 13th CGPM (Resolution 1).

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