content: /* ========================================================================
   * JCommon : a free general purpose class library for the Java(tm) platform
   * ========================================================================
   *
   * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
   * 
   * Project Info:  http://www.jfree.org/jcommon/index.html
   *
   * This library is free software; you can redistribute it and/or modify it 
   * under the terms of the GNU Lesser General Public License as published by 
   * the Free Software Foundation; either version 2.1 of the License, or 
   * (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful, but 
   * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
   * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
   * License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
   * USA.  
   *
   * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
   * in the United States and other countries.]
   *
   * ---------------------
   * EasterSundayRule.java
   * ---------------------
   * (C) Copyright 2000-2003, by Object Refinery Limited.
   *
   * Original Author:  David Gilbert (for Object Refinery Limited);
   * Contributor(s):   -;
   *
   * $Id: EasterSundayRule.java,v 1.4 2005/11/16 15:58:40 taqua Exp $
   *
   * Changes (from 26-Oct-2001)
   * --------------------------
   * 26-Oct-2001 : Changed package to com.jrefinery.date.*;
   * 03-Oct-2002 : Fixed errors reported by Checkstyle (DG);
   * 01-Jun-2005 : Removed the explicit clonable declaration, it is declared
   *               in the super class.
   */
  
  package org.jfree.date;
  
  /**
   * An annual date rule for Easter (Sunday).  The algorithm used here was
   * obtained from a Calendar FAQ which can be found at:
   * <P>
   * <a href="http://www.tondering.dk/claus/calendar.html"
   *     >http://www.tondering.dk/claus/calendar.html</a>.
   * <P>
   * It is based on an algorithm by Oudin (1940) and quoted in "Explanatory Supplement to the
   * Astronomical Almanac", P. Kenneth Seidelmann, editor.
   *
   * @author David Gilbert
   */
  public class EasterSundayRule extends AnnualDateRule {
  
      /**
       * Default constructor.
       */
      public EasterSundayRule() {
      }
  
      /**
       * Returns the date of Easter Sunday for the given year.  See the class
       * description for the source of the algorithm.
       * <P>
       * This method supports the AnnualDateRule interface.
       *
       * @param year  the year to check.
       *
       * @return the date of Easter Sunday for the given year.
       */
      public SerialDate getDate(final int year) {
          final int g = year % 19;
          final int c = year / 100;
          final int h = (c - c / 4 - (8 * c + 13) / 25 + 19 * g + 15) % 30;
          final int i = h - h / 28 * (1 - h / 28 * 29 / (h + 1) * (21 - g) / 11);
          final int j = (year + year / 4 + i + 2 - c + c / 4) % 7;
          final int l = i - j;
          final int month = 3 + (l + 40) / 44;
          final int day = l + 28 - 31 * (month / 4);
          return SerialDate.createInstance(day, month, year);
      }
  
  }
  