Skip to main navigation menu Skip to main content Skip to site footer


1972: Vol. XLIX, No. 2

The Improved UTC System to be Introduced on 1 January 1972

  • J. McA. Steele
August 11, 2015


Following the introduction of the system of Coordinated Universal Time (UTC) the majority of time signal emissions throughout the world have operated on an atomic basis for the past ten years. However the stations participating in this system do not radiate Atomic Time (AT) but an approximation to Universal Time (UT2) achieved by applying an offset to the time signal generator. This compromise arrangement will shortly be replaced by an 'improved UTC system' (*) in which the offset will be eliminated and the interval between successive pulses will truly represent the basic unit of time, the second of the 'Système International d’Unités', commonly called the SI system in English. Overall agreement with astronomical time will now be maintained by step adjustments of amount exactly one second applied, when necessary, once or twice per year. These will restrict the excursion between UTC and the time scale UT1 to less than 0.7 second and the magnitude and sense of the difference (UT1 — UTC) will be indicated by means of a coded announcement radiated with the time signals.