#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"
  subtype:  lunar_calendar  lunisolar_calendar  solar_calendar
  part:  intercalation  an insertion into a calendar

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