---
metadata:
  title: CIPM, 1956
  date: '1956-01-01'
  source: BIPM - Pavillon de Breteuil
resolutions:
- dates:
  - '1956-01-01'
  title: Definition of the unit of time (second)
  identifier: 1
  url: https://www.bipm.org/en/CIPM/db/1956/1/
  approvals:
  - type: affirmative
    degree: unanimous
    message: |-
      +

      In virtue of the powers invested in it by cgpm-resolution:en/10/5[Resolution 5] of the 10th Conférence Générale des Poids et Mesures, the Comité International des Poids et Mesures,
  considerations:
  - type: considering
    date_effective: '1956-01-01'
    message: considering that the 9th General Assembly of the International Astronomical
      Union (Dublin, 1955) declared itself in favour of linking the second to the
      tropical year,
  - type: considering
    date_effective: '1956-01-01'
    message: |-
      considering 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) ´ stem:[10^(-9)] of the tropical year for 1900 January 0 at stem:[12 "h"] ET,
  actions:
  - type: decides
    date_effective: '1956-01-01'
    message: decides "The second is the fraction 1/31 556 925.9747 of the tropical
      year for 1900 January 0 at 12 hours ephemeris time."