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."

    Comptes rendus de la 11e CGPM (1960), 1961, 86


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