75 lines
2.3 KiB
C
75 lines
2.3 KiB
C
/* $OpenBSD: ostern.c,v 1.10 2024/04/23 13:34:50 jsg Exp $ */
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/*
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* Copyright (c) 1996 Wolfram Schneider <wosch@FreeBSD.org>. Berlin.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <stdio.h>
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#include <time.h>
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#include "calendar.h"
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/* return year day for Easter */
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int
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easter(int year) /* 0 ... abcd, NOT since 1900 */
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{
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int e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k;
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int e_l, e_m, e_n, e_p, e_q;
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/* silly, but it works */
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e_a = year % 19;
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e_b = year / 100;
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e_c = year % 100;
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e_d = e_b / 4;
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e_e = e_b % 4;
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e_f = (e_b + 8) / 25;
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e_g = (e_b + 1 - e_f) / 3;
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e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30;
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e_i = e_c / 4;
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e_k = e_c % 4;
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e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7;
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e_m = (e_a + 11 * e_h + 22 * e_l) / 451;
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e_n = (e_h + e_l + 114 - (7 * e_m)) / 31;
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e_p = (e_h + e_l + 114 - (7 * e_m)) % 31;
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e_p = e_p + 1;
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e_q = 31 + 28 + e_p;
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if (isleap(year))
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e_q++;
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if (e_n == 4)
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e_q += 31;
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#if DEBUG
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printf("%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d\n",
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e_a, e_b, e_c, e_d, e_e, e_f, e_g, e_h,
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e_i, e_k, e_l, e_m, e_n, e_p, e_q);
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#endif
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return (e_q);
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}
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