ostern.c revision 15720
1/* 2 * Copyright (c) 1995 Wolfram Schneider. Public domain. 3 * 4 * $Id: ostern.c,v 1.2 1996/05/10 16:29:42 ache Exp $ 5*/ 6 7#include <string.h> 8#include <stdlib.h> 9#include <stdio.h> 10 11#include "calendar.h" 12 13/* return year day for Easter */ 14 15int easter (year) 16 int year; /* 0 ... abcd, NOT since 1900 */ 17{ 18 19 int e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k, 20 e_l, e_m, e_n, e_p, e_q; 21 22 /* silly, but it works */ 23 e_a = year % 19; 24 e_b = year / 100; 25 e_c = year % 100; 26 27 e_d = e_b / 4; 28 e_e = e_b % 4; 29 e_f = (e_b + 8) / 25; 30 e_g = (e_b + 1 - e_f) / 3; 31 e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30; 32 e_i = e_c / 4; 33 e_k = e_c % 4; 34 e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7; 35 e_m = (e_a + 11 * e_h + 22 * e_l) / 451; 36 e_n = (e_h + e_l + 114 - (7 * e_m)) / 31; 37 e_p = (e_h + e_l + 114 - (7 * e_m)) % 31; 38 e_p = e_p + 1; 39 40 e_q = 31 + 28; 41 42 if (e_k == 0 && e_c != 0) 43 e_q += 1; 44 45 if (e_n == 4) 46 e_q += 31; 47 48 e_q += e_p; 49 50#if DEBUG 51 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); 52#endif 53 54 return (e_q); 55} 56 57/* return year day for Easter or easter depending days 58 * Match: Easter([+-][0-9]+)? 59 * e.g: Easter-2 is Good Friday (2 days before Easter) 60 */ 61 62int 63geteaster(s, year) 64 char *s; 65 int year; 66{ 67 register int offset = 0; 68 extern struct fixs neaster; 69 70#define EASTER "easter" 71#define EASTERNAMELEN (sizeof(EASTER) - 1) 72 73 if (strncasecmp(s, EASTER, EASTERNAMELEN) == 0) 74 s += EASTERNAMELEN; 75 else if ( neaster.name != NULL 76 && strncasecmp(s, neaster.name, neaster.len) == 0 77 ) 78 s += neaster.len; 79 else 80 return(0); 81 82#if DEBUG 83 printf("%s %d %d\n", s, year, EASTERNAMELEN); 84#endif 85 86 /* Easter+1 or Easter-2 87 * ^ ^ */ 88 89 switch(*s) { 90 91 case '-': 92 case '+': 93 offset = atoi(s); 94 break; 95 96 default: 97 offset = 0; 98 } 99 100 return (easter(year) + offset); 101} 102