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/* $OpenBSD: ostern.c,v 1.7 2009/10/27 23:59:36 deraadt Exp $ */
/*
* Copyright (c) 1996 Wolfram Schneider <wosch@FreeBSD.org>. Berlin.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $Id: ostern.c,v 1.7 2009/10/27 23:59:36 deraadt Exp $
*/
#include <stdio.h>
#include <time.h>
#include <tzfile.h>
#include "calendar.h"
/* return year day for Easter */
int
easter(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;
int 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 + e_p;
if (isleap(year))
e_q++;
if (e_n == 4)
e_q += 31;
#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);
}
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