1 /* $OpenBSD: ostern.c,v 1.8 2015/03/15 00:41:28 millert 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 1.8 2015/03/15 00:41:28 millert Exp $ 29 */ 30 31 #include <stdio.h> 32 #include <time.h> 33 34 #include "calendar.h" 35 36 /* return year day for Easter */ 37 38 int 39 easter(int year) /* 0 ... abcd, NOT since 1900 */ 40 { 41 int e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k; 42 int e_l, e_m, e_n, e_p, e_q; 43 44 /* silly, but it works */ 45 e_a = year % 19; 46 e_b = year / 100; 47 e_c = year % 100; 48 49 e_d = e_b / 4; 50 e_e = e_b % 4; 51 e_f = (e_b + 8) / 25; 52 e_g = (e_b + 1 - e_f) / 3; 53 e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30; 54 e_i = e_c / 4; 55 e_k = e_c % 4; 56 e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7; 57 e_m = (e_a + 11 * e_h + 22 * e_l) / 451; 58 e_n = (e_h + e_l + 114 - (7 * e_m)) / 31; 59 e_p = (e_h + e_l + 114 - (7 * e_m)) % 31; 60 e_p = e_p + 1; 61 62 e_q = 31 + 28 + e_p; 63 if (isleap(year)) 64 e_q++; 65 66 if (e_n == 4) 67 e_q += 31; 68 69 #if DEBUG 70 printf("%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d\n", 71 e_a, e_b, e_c, e_d, e_e, e_f, e_g, e_h, 72 e_i, e_k, e_l, e_m, e_n, e_p, e_q); 73 #endif 74 75 return (e_q); 76 } 77