Resolution 1 of the 46th CIPM (1956)
Definition of the unit of time (second)
In virtue of the powers invested in it by Resolution 5 of the 10th Conférence Générale des Poids et Mesures, the Comité International des Poids et Mesures,
- that the 9th General Assembly of the International Astronomical Union (Dublin, 1955) declared itself in favour of linking the second to the tropical year,
- that, according to the decisions of the 8th General Assembly of the International Astronomical Union (Rome, 1952), the second of ephemeris time (ET) is the fraction
(12 960 276 813 / 408 986 496)× 10−9 of the tropical year for 1900 January 0 at 12 h ET,
- “The second is the fraction 1/31 556 925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time.”
This definition was abrogated in 1967 by the 13th CGPM (Resolution 1).