Compute easter date for a given year from 1583, using Lilius/Clavius algorithm.
Actually the Gregorian easter Sunday date.
In many countries, those of Christian traditions, some public holidays depend on easter date. The date of this movable feast is defined to be the first Sunday that follows the 14th day of moon (full moon) that occurs on March 21 or just after; where the days of moon are not determined by astronomical observations but by a computed calendar.
In the context of the Gregorian calendar reform, mathematician Clavius established, from previous works of astronomer Lilius, the method for computing the easter date.
This program, written in C++11, use this algorithm to compute the easter date for any year from 1583. The Gregorian calendar was instituted in October 1582, and easter falls either in March or in April, so the first year for which a Gregorian easter date can be computed is 1583.
For unit tests, boost version 1.59 or higher is required.
Licensed under GPLv3.