Easter

🐰

Algorithms to calculate the date of Easter Sunday: namespace Timely\Easter, Java package timely.easter.

Calculator.java

1. Butcher's Algorithm (easterSundayButcher)

   • Calculates Easter Sunday in the Gregorian calendar using Butcher's explicit formula.
   • Input: int year
   • Output: int[] in format [day, month, year]

2. Oudin's Algorithm (easterSundayOudin)

   • Alternative astronomical/mathematical method for calculating Easter Sunday in the Gregorian calendar.
   • Input: int year
   • Output: int[] in format [day, month, year]

3. Meeus's Algorithm (easterSundayMeeus)

   • Calculates Easter Sunday in the Julian calendar.
   • Input: int year
   • Output: int[] in format [day, month, year]

Calculator.php

• Calculator::sunday(?int $year): Returns Easter Sunday as a DateTime. Uses easter_days() when the calendar extension is installed, otherwise Butcher's algorithm.
• Calculator::friday(?int $year) and Calculator::monday(?int $year): Good Friday and Easter Monday.
• Calculator::sundayButcher(int $year): Butcher's algorithm ported to PHP.

use Timely\Easter\Calculator;

Calculator::sunday(2026)->format("j.n.Y"); // "5.4.2026"

Calculator.js

JavaScript class Timely.Calculator with sundayOudin(year), friday(year) and monday(year), each returning a Converter; see JavaScript.

Try it in the Examples (examples/easter.html). The Holidays use EasterCalculator for holidays relative to Easter.