Gregorian calendar It also specifies its epact relative to 1 January, in contrast with the Julian calendar, which specified it relative to 22 March. The old date was derived from the Greek system: the earlier "Supputatio Romana" specified it relative to 1 January. During the period between 1582, when the first countries adopted the Gregorian calendar, and 1923, when the last European country adopted it, it was often necessary to indicate the date of some event in both the Julian calendar and in the Gregorian calendar, for example, "10/21 February 1750/51", where the dual year accounts for some countries already beginning their
Berber calendar of Mauretania Caesariensis and the Roman province of Africa, as it is a surviving form of the Julian calendar. The latter calendar was used in Europe before the adoption of the Gregorian calendar, with month names derived from Latin. Berber populations previously used various indigenous calendars, such as that of the Guanche autochthones of the Canary Islands. However, relatively little is known of these ancient calendrical systems. The agricultural Berber calendar still in use is almost certainly derived from the Julian calendar, introduced in the Roman province of Africa at the time of Roman domination. The names of the months