**Calendars:**

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 (the calculation is known as Computus) 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.