Showing posts with label Donald Knuth. Show all posts
Showing posts with label Donald Knuth. Show all posts

Thursday, March 24, 2016

Computing the date of Easter

Raphael - Resurrection of Christ
The first Ecumenical Council was held in Nicaea, Asia Minor, in 325, convened by Emperor Constantine. Ecumenical councils could not be held before that date, for Christians were persecuted and had to meet in secret. This first Council had very important consequences: Aryanism, which denied the divinity of Christ, was condemned; the version of the creed still recited in mass today was defined; and the Council established the algorithm to calculate the date of Easter, which is still in use. This algorithm is so complicated that Donald Knuth included a program to perform it in his famous and classic computer encyclopedia, The Art of Computer Programming.
Easter was fixed on the first Sunday after the first full moon after the spring equinox, which that year fell in March 21st. To calculate the exact date one must take into account that the solar cycle (the year) contains 365.2421988 days, while the lunar cycle (the phases of the moon) lasts 29.530588 days, two numbers with many figures that do not have a simple relationship with one another, so the calculation is quite complex.