/*
* Copyright (c) 1995 Wolfram Schneider. Public domain.
*
* $Id: ostern.c,v 1.2 1996/02/01 13:05:12 wosch Exp $
*/
#include <string.h>
/* return year day for Easter */
int easter (year)
int year; /* 0 ... abcd, NOT since 1900 */
{
int 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;
/* silly, but it works */
e_a = year % 19;
e_b = year / 100;
e_c = year % 100;
e_d = e_b / 4;
e_e = e_b % 4;
e_f = (e_b + 8) / 25;
e_g = (e_b + 1 - e_f) / 3;
e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30;
e_i = e_c / 4;
e_k = e_c % 4;
e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7;
e_m = (e_a + 11 * e_h + 22 * e_l) / 451;
e_n = (e_h + e_l + 114 - (7 * e_m)) / 31;
e_p = (e_h + e_l + 114 - (7 * e_m)) % 31;
e_p = e_p + 1;
e_q = 31 + 28;
if (e_k == 0 && e_c != 0)
e_q += 1;
if (e_n == 4)
e_q += 31;
e_q += e_p;
#if DEBUG
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);
#endif
return (e_q);
}
/* return year day for Easter or easter depending days
* Match: Easter([+-][0-9]+)?
* e.g: Easter-2 is Good Friday (2 days before Easter)
*/
int
geteaster(s, year)
char *s;
int year;
{
register int offset = 0;
#define EASTER "easter"
#define EASTERNAMELEN (sizeof(EASTER) - 1)
/* no easter */
if (strncasecmp(s, EASTER, EASTERNAMELEN))
return(0);
#if DEBUG
printf("%s %d %d\n", s, year, EASTERNAMELEN);
#endif
/* Easter+1 or Easter-2
* ^ ^ */
switch(*(s + EASTERNAMELEN)) {
case '-':
offset = -(atoi(s + EASTERNAMELEN + 1));
break;
case '+':
offset = atoi(s + EASTERNAMELEN + 1);
break;
default:
offset = 0;
}
return (easter(year) + offset);
}
