Calendrical Calculation

A calendrical calculation is a computation concerning calendar dates, a branch of applied mathematics covering several standard problems: converting a date in the Julian or Gregorian calendar to and from a Julian day number for a standardized representation, finding the interval in days between two dates by differencing their Julian day numbers, determining the date of a moveable holiday such as Easter through the process called Computus, Pentecost or Passover, converting a date between different calendar systems, for example the Kuwaiti algorithm for converting Gregorian to Islamic calendar dates, and calculating which day of the week corresponds to a given date. These calculations underlie the practical generation of calendars and religious or civil observance schedules; calendrical calculation is also noted as one of the five characteristic skills associated with savant syndrome, reflecting the cognitive demands some of these computations place on unaided mental arithmetic. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/