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Understanding > Astronomical calculations > Calendars V


for a date included between January 1, -4000 and Decembre 31, 2500

If the date is earlier or equal to Octobre 4, 1582, this date is a date of the Julian Calendar. If the date later or eqaul to Octobre 15, 1582, this date is a date of the Gregorian Calendar.   For the years before Christ, use the notation of the astronomers: 1 year before J.C. = year 0).

   the               is a  

   Number of days: 

The number of each day inside a year is provided from 1567.
The standard numbers of the weeks start in 1976.
Recommandations International Organisation of Standards : 

    - Monday is considered as the first day of the week.
    - The weeks of a year are numbered 01 to 52 (sometimes 53).
    - The week numbered 01 is the week including the first Thurday of January.
    - It happens that the week 53 exists: common year ending on a Thursday or leap year ending on a Thursday or a Friday).
Credit : P. Rocher/G. Satre/J.E. Arlot/IMCCE/CNRS