A Calendrical calculation is a calculation concerning calendar dates. Calendrical calculations can be considered an area of applied mathematics. Some examples of calendrical calculations: * The number of days between two dates. * The date of a religious holiday, like Easter or Passover, for a given year. * Converting a date between different calendars. For instance, dates in the Gregorian calendar can be converted to dates in the Islamic calendar with the Kuwaiti algorithm. * Calculating the day of the week.