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Understanding > Astronomical calculations > Legal time


The Legal Time or time in use in France is determinated from the Coordinated Universal Time (UTC). From 1911 until nowadays, the dates for the change of time (daylight time) were decided by official decree. It was not always the same regulations, depending on the politics. When changes occur, for summer time, we have to add one hour on the clocks, and, to go back to winter time, we have to substract one hour on the clocks.

At the present time (February 2016), the official decree determining daylight time and standard time (summer and winter time) goes only until 2021.

  YEAR (between 1911 and 2021) :     


Credit : P. Rocher/G. Satre/IMCCE/CNRS

Click here for the definition of the Legal time