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Perpetual calendar

This activity belongs to the GeoGebra book Earth and Sun. Choose the year you want to display. It supports from year 1 to year 9999.
  • Leap years are multiples of 400 or, starting from year 8, multiples of 4 that are not multiples of 100 (year 4 was not a leap year, by order of the first Roman emperor, Augustus, to correct previous discrepancies).
  • In 1582 (90 years after the discovery of America) the Julian calendar was changed to the Gregorian calendar, eliminating 10 days from October.
Author of the construction of GeoGebra: Rafael Losada