The agenda uses an algorithm unpaid to J.M.Oudin (1940), which calculates the Sunday on which Easter choice descent according to the earliest ecclesiastical filled planet on or following March 21.

This use, Easter, was inspired by a accidental social call to the U.S. Naval Observatory, Astronomical Applications Section (http://aa.usno.navy.mil/faq/docs/easter.html), when a collection of friends were wondering when Easter opening would be this year.

In the UK Easter opening is a paid four-light extended-weekend. But it is clumsy to scheme for because the time is not permanent. Maybe this agenda choice assistance you get the excellent from Easter Opening from now on.