1 /* $OpenBSD: paskha.c,v 1.4 2004/12/10 15:31:01 mickey Exp $ */ 2 3 /* 4 * Copyright (C) 1993-1996 by Andrey A. Chernov, Moscow, Russia. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #ifndef lint 30 static const char rcsid[] = "$OpenBSD: paskha.c,v 1.4 2004/12/10 15:31:01 mickey Exp $"; 31 #endif /* not lint */ 32 33 #include <stdio.h> 34 #include <tzfile.h> 35 36 #include "calendar.h" 37 38 /* return year day for Orthodox Easter using Gauss formula */ 39 /* (new style result); subtract 13 for old style */ 40 41 int 42 paskha (R) 43 int R; /*year*/ 44 { 45 int a, b, c, d, e; 46 static int x = 15; 47 static int y = 6; 48 int cumdays; 49 50 a = R % 19; 51 b = R % 4; 52 c = R % 7; 53 d = (19*a + x) % 30; 54 e = (2*b + 4*c + 6*d + y) % 7; 55 cumdays = 31 + 28; 56 if (isleap(R)) 57 cumdays++; 58 return ((cumdays + 22) + (d + e) + 13); 59 } 60