QBasic Math Tools and Utilities

Clavius-Lilius Algorithm to compute date of Easter Sunday for any year since 1582 in the Gregorian Calendar
During the Middle Ages, nearly the only use Christian Europe had for arithmetic was to compute the date of Easter. Therefore, the Easter problem has historical as well as religious, astronomical and mathematical significance.
The problem involves translating between the ancient Jewish lunar calendar and the modern solar Gregorian calendar, because the Resurrection came three days after the Last Supper -- the feast of Passover.
In most Western churches, Easter is the first Sunday after the Paschal Full Moon -- no longer an actual full moon, but a computed full moon in early Spring based on the 19-year Metonic lunar cycle. Most Christian authorities agreed to this method at the Council of Nicea (in modern Turkey) in 325.
With the introduction of the reformed Gregorian Calendar in 1582, the modern method for computing Easter was developed by the German Jesuit mathematician Christopher Clavius and the Neapolitan astronomer Aloysius Lilius.