#calendar.organisation  a system of timekeeping that defines the beginning and length and divisions of the year
  supertype:  #organisation__arrangement__organization__system  an organized structure for arranging or classifying; "he changed the arrangement of the topics"; "the facts were familiar but it was in the organization of them that he was original"; "he tried to understand their system of classification"
  part:  #intercalation
  subtype:  #lunar_calendar__lunarcalendar  a calendar based on lunar cycles
     subtype:  #Muhammadan_calendar__Mohammedan_calendar__Moslem_calendar__Muslim_calendar  the lunar calendar used by Moslems; dates from 622 AD (the year of the Hegira); the beginning of the Moslem year retrogresses through the solar year completing the cycle every 32 years
     instance:  #Roman_calendar
  subtype:  #lunisolar_calendar__lunisolarcalendar  a calendar based on both lunar and solar cycles
     subtype:  #Jewish_calendar__Hebrew_calendar__hebrewcalendar  (Judaism) the calendar used by the Jews; dates from 3761 BC (the assumed date of the creation of the world); a lunar year of 354 days is adjusted to the solar year by periodic leap years
     subtype:  #Hindu_calendar  the lunisolar calendar governing the religious life of Hindus; an extra month is inserted after every month in which there are two new moons (once every three years)
  subtype:  #solar_calendar__solarcalendar  a calendar based on solar cycles
     subtype:  #Gregorian_calendar__New_Style  the solar calendar now in general use, introduced by Pope Gregory XIII in 1582 AD to correct an error in the Julian calendar by suppressing 10 days, making Oct 5 be called Oct 15, and providing that only centenary years divisible by 400 should be leap years; it was adopted by Great Britain and the American colonies in 1752
        subtype:  #church_calendar__ecclesiastical_calendar  a calendar of the Christian year indicating the dates of fasts and festivals
     subtype:  #Julian_calendar__Old_Style  the solar calendar introduced in Rome in 46 b.c. by Julius Caesar and slightly modified by Augustus, establishing the 12-month year of 365 days with each 4th year having 366 days and the months having 31 or 30 days except for February
     subtype:  #Revolutionary_calendar  the calendar adopted by The French First Republic in 1793 and abandoned in 1805; dates were calculated from Sept. 22, 1792

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