1 /* $OpenBSD: ostern.c,v 1.7 2009/10/27 23:59:36 deraadt Exp $ */ 2 3 /* 4 * Copyright (c) 1996 Wolfram Schneider <wosch@FreeBSD.org>. Berlin. 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 AND CONTRIBUTORS ``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 AUTHOR 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 * $Id: ostern.c,v 1.7 2009/10/27 23:59:36 deraadt Exp $ 29 */ 30 31 #include <stdio.h> 32 #include <time.h> 33 #include <tzfile.h> 34 35 #include "calendar.h" 36 37 /* return year day for Easter */ 38 39 int 40 easter(int year) /* 0 ... abcd, NOT since 1900 */ 41 { 42 int e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k; 43 int e_l, e_m, e_n, e_p, e_q; 44 45 /* silly, but it works */ 46 e_a = year % 19; 47 e_b = year / 100; 48 e_c = year % 100; 49 50 e_d = e_b / 4; 51 e_e = e_b % 4; 52 e_f = (e_b + 8) / 25; 53 e_g = (e_b + 1 - e_f) / 3; 54 e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30; 55 e_i = e_c / 4; 56 e_k = e_c % 4; 57 e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7; 58 e_m = (e_a + 11 * e_h + 22 * e_l) / 451; 59 e_n = (e_h + e_l + 114 - (7 * e_m)) / 31; 60 e_p = (e_h + e_l + 114 - (7 * e_m)) % 31; 61 e_p = e_p + 1; 62 63 e_q = 31 + 28 + e_p; 64 if (isleap(year)) 65 e_q++; 66 67 if (e_n == 4) 68 e_q += 31; 69 70 #if DEBUG 71 printf("%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d\n", 72 e_a, e_b, e_c, e_d, e_e, e_f, e_g, e_h, 73 e_i, e_k, e_l, e_m, e_n, e_p, e_q); 74 #endif 75 76 return (e_q); 77 } 78