ostern.c revision 13840
113840Swosch/* 213840Swosch * Copyright (c) 1995 Wolfram Schneider. Public domain. 313840Swosch * 413840Swosch * $Id: ostern.c,v 1.2 1996/02/01 13:05:12 wosch Exp $ 513840Swosch*/ 613840Swosch 713840Swosch#include <string.h> 813840Swosch 913840Swosch/* return year day for Easter */ 1013840Swosch 1113840Swoschint easter (year) 1213840Swosch int year; /* 0 ... abcd, NOT since 1900 */ 1313840Swosch{ 1413840Swosch 1513840Swosch int e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k, 1613840Swosch e_l, e_m, e_n, e_p, e_q; 1713840Swosch 1813840Swosch /* silly, but it works */ 1913840Swosch e_a = year % 19; 2013840Swosch e_b = year / 100; 2113840Swosch e_c = year % 100; 2213840Swosch 2313840Swosch e_d = e_b / 4; 2413840Swosch e_e = e_b % 4; 2513840Swosch e_f = (e_b + 8) / 25; 2613840Swosch e_g = (e_b + 1 - e_f) / 3; 2713840Swosch e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30; 2813840Swosch e_i = e_c / 4; 2913840Swosch e_k = e_c % 4; 3013840Swosch e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7; 3113840Swosch e_m = (e_a + 11 * e_h + 22 * e_l) / 451; 3213840Swosch e_n = (e_h + e_l + 114 - (7 * e_m)) / 31; 3313840Swosch e_p = (e_h + e_l + 114 - (7 * e_m)) % 31; 3413840Swosch e_p = e_p + 1; 3513840Swosch 3613840Swosch e_q = 31 + 28; 3713840Swosch 3813840Swosch if (e_k == 0 && e_c != 0) 3913840Swosch e_q += 1; 4013840Swosch 4113840Swosch if (e_n == 4) 4213840Swosch e_q += 31; 4313840Swosch 4413840Swosch e_q += e_p; 4513840Swosch 4613840Swosch#if DEBUG 4713840Swosch 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); 4813840Swosch#endif 4913840Swosch 5013840Swosch return (e_q); 5113840Swosch} 5213840Swosch 5313840Swosch/* return year day for Easter or easter depending days 5413840Swosch * Match: Easter([+-][0-9]+)? 5513840Swosch * e.g: Easter-2 is Good Friday (2 days before Easter) 5613840Swosch */ 5713840Swosch 5813840Swoschint 5913840Swoschgeteaster(s, year) 6013840Swosch char *s; 6113840Swosch int year; 6213840Swosch{ 6313840Swosch register int offset = 0; 6413840Swosch 6513840Swosch#define EASTER "easter" 6613840Swosch#define EASTERNAMELEN (sizeof(EASTER) - 1) 6713840Swosch 6813840Swosch /* no easter */ 6913840Swosch if (strncasecmp(s, EASTER, EASTERNAMELEN)) 7013840Swosch return(0); 7113840Swosch 7213840Swosch#if DEBUG 7313840Swosch printf("%s %d %d\n", s, year, EASTERNAMELEN); 7413840Swosch#endif 7513840Swosch 7613840Swosch /* Easter+1 or Easter-2 7713840Swosch * ^ ^ */ 7813840Swosch 7913840Swosch switch(*(s + EASTERNAMELEN)) { 8013840Swosch 8113840Swosch case '-': 8213840Swosch offset = -(atoi(s + EASTERNAMELEN + 1)); 8313840Swosch break; 8413840Swosch 8513840Swosch case '+': 8613840Swosch offset = atoi(s + EASTERNAMELEN + 1); 8713840Swosch break; 8813840Swosch 8913840Swosch default: 9013840Swosch offset = 0; 9113840Swosch } 9213840Swosch 9313840Swosch return (easter(year) + offset); 9413840Swosch} 95