ostern.c revision 15737
1/* 2 * Copyright (c) 1995 Wolfram Schneider. Public domain. 3 * 4 * $Id: ostern.c,v 1.3 1996/05/10 17:32:05 ache Exp $ 5*/ 6 7#include <stdio.h> 8#include <stdlib.h> 9#include <string.h> 10#include <time.h> 11 12#include "calendar.h" 13 14/* return year day for Easter */ 15 16int easter (year) 17 int year; /* 0 ... abcd, NOT since 1900 */ 18{ 19 20 int e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k, 21 e_l, e_m, e_n, e_p, e_q; 22 23 /* silly, but it works */ 24 e_a = year % 19; 25 e_b = year / 100; 26 e_c = year % 100; 27 28 e_d = e_b / 4; 29 e_e = e_b % 4; 30 e_f = (e_b + 8) / 25; 31 e_g = (e_b + 1 - e_f) / 3; 32 e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30; 33 e_i = e_c / 4; 34 e_k = e_c % 4; 35 e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7; 36 e_m = (e_a + 11 * e_h + 22 * e_l) / 451; 37 e_n = (e_h + e_l + 114 - (7 * e_m)) / 31; 38 e_p = (e_h + e_l + 114 - (7 * e_m)) % 31; 39 e_p = e_p + 1; 40 41 e_q = 31 + 28; 42 43 if (e_k == 0 && e_c != 0) 44 e_q += 1; 45 46 if (e_n == 4) 47 e_q += 31; 48 49 e_q += e_p; 50 51#if DEBUG 52 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); 53#endif 54 55 return (e_q); 56} 57 58/* return year day for Easter or easter depending days 59 * Match: Easter([+-][0-9]+)? 60 * e.g: Easter-2 is Good Friday (2 days before Easter) 61 */ 62 63int 64geteaster(s, year) 65 char *s; 66 int year; 67{ 68 register int offset = 0; 69 extern struct fixs neaster; 70 71#define EASTER "easter" 72#define EASTERNAMELEN (sizeof(EASTER) - 1) 73 74 if (strncasecmp(s, EASTER, EASTERNAMELEN) == 0) 75 s += EASTERNAMELEN; 76 else if ( neaster.name != NULL 77 && strncasecmp(s, neaster.name, neaster.len) == 0 78 ) 79 s += neaster.len; 80 else 81 return(0); 82 83#if DEBUG 84 printf("%s %d %d\n", s, year, EASTERNAMELEN); 85#endif 86 87 /* Easter+1 or Easter-2 88 * ^ ^ */ 89 90 switch(*s) { 91 92 case '-': 93 case '+': 94 offset = atoi(s); 95 break; 96 97 default: 98 offset = 0; 99 } 100 101 return (easter(year) + offset); 102} 103