ostern.c revision 13840
1127474Stjr/* 2127474Stjr * Copyright (c) 1995 Wolfram Schneider. Public domain. 3127474Stjr * 4127474Stjr * $Id: ostern.c,v 1.2 1996/02/01 13:05:12 wosch Exp $ 5127474Stjr*/ 6174990Sache 7127474Stjr#include <string.h> 8127474Stjr 9127474Stjr/* return year day for Easter */ 10127474Stjr 11127474Stjrint easter (year) 12127474Stjr int year; /* 0 ... abcd, NOT since 1900 */ 13127474Stjr{ 14127474Stjr 15127474Stjr int e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k, 16127474Stjr e_l, e_m, e_n, e_p, e_q; 17127474Stjr 18127474Stjr /* silly, but it works */ 19127474Stjr e_a = year % 19; 20127474Stjr e_b = year / 100; 21174990Sache e_c = year % 100; 22127474Stjr 23127474Stjr e_d = e_b / 4; 24127474Stjr e_e = e_b % 4; 25127474Stjr e_f = (e_b + 8) / 25; 26127474Stjr e_g = (e_b + 1 - e_f) / 3; 27127474Stjr e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30; 28127474Stjr e_i = e_c / 4; 29127474Stjr e_k = e_c % 4; 30127474Stjr e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7; 31127474Stjr e_m = (e_a + 11 * e_h + 22 * e_l) / 451; 32127474Stjr e_n = (e_h + e_l + 114 - (7 * e_m)) / 31; 33127474Stjr e_p = (e_h + e_l + 114 - (7 * e_m)) % 31; 34127474Stjr e_p = e_p + 1; 35127474Stjr 36174990Sache e_q = 31 + 28; 37127474Stjr 38127474Stjr if (e_k == 0 && e_c != 0) 39127474Stjr e_q += 1; 40127474Stjr 41127474Stjr if (e_n == 4) 42127474Stjr e_q += 31; 43127474Stjr 44127474Stjr e_q += e_p; 45127474Stjr 46174990Sache#if DEBUG 47127474Stjr printf("%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d\n", e_a , e_b , e_c , e_d , e_e , e_f , e_g , e_h , e_i , e_k , e_l , e_m , e_n , e_p , e_q); 48127474Stjr#endif 49127474Stjr 50127474Stjr return (e_q); 51127474Stjr} 52127474Stjr 53127474Stjr/* return year day for Easter or easter depending days 54127474Stjr * Match: Easter([+-][0-9]+)? 55127474Stjr * e.g: Easter-2 is Good Friday (2 days before Easter) 56127474Stjr */ 57127474Stjr 58127474Stjrint 59127474Stjrgeteaster(s, year) 60127474Stjr char *s; 61127474Stjr int year; 62127474Stjr{ 63127474Stjr register int offset = 0; 64127474Stjr 65127474Stjr#define EASTER "easter" 66127474Stjr#define EASTERNAMELEN (sizeof(EASTER) - 1) 67127474Stjr 68127474Stjr /* no easter */ 69127474Stjr if (strncasecmp(s, EASTER, EASTERNAMELEN)) 70127474Stjr return(0); 71127474Stjr 72127474Stjr#if DEBUG 73127474Stjr printf("%s %d %d\n", s, year, EASTERNAMELEN); 74127474Stjr#endif 75127474Stjr 76127474Stjr /* Easter+1 or Easter-2 77127474Stjr * ^ ^ */ 78127474Stjr 79127474Stjr switch(*(s + EASTERNAMELEN)) { 80174990Sache 81127474Stjr case '-': 82127474Stjr offset = -(atoi(s + EASTERNAMELEN + 1)); 83127474Stjr break; 84127474Stjr 85127474Stjr case '+': 86127474Stjr offset = atoi(s + EASTERNAMELEN + 1); 87127474Stjr break; 88127474Stjr 89127474Stjr default: 90127474Stjr offset = 0; 91127474Stjr } 92127474Stjr 93127474Stjr return (easter(year) + offset); 94127474Stjr} 95127474Stjr