paskha.c revision 205821 
1285SN/A/*-
2462SN/A * Copyright (C) 1993-1996 by Andrey A. Chernov, Moscow, Russia.
3285SN/A * All rights reserved.
4285SN/A *
5285SN/A * Redistribution and use in source and binary forms, with or without
6285SN/A * modification, are permitted provided that the following conditions
7285SN/A * are met:
8285SN/A * 1. Redistributions of source code must retain the above copyright
9285SN/A *    notice, this list of conditions and the following disclaimer.
10285SN/A * 2. Redistributions in binary form must reproduce the above copyright
11285SN/A *    notice, this list of conditions and the following disclaimer in the
12285SN/A *    documentation and/or other materials provided with the distribution.
13285SN/A *
14285SN/A * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
15285SN/A * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16285SN/A * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17285SN/A * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
18285SN/A * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19285SN/A * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20285SN/A * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21285SN/A * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22285SN/A * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23285SN/A * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24285SN/A * SUCH DAMAGE.
25285SN/A */
26285SN/A
27285SN/A#include <sys/cdefs.h>
28285SN/A__FBSDID("$FreeBSD: head/usr.bin/calendar/paskha.c 205821 2010-03-29 06:49:20Z edwin $");
29285SN/A
30285SN/A#include <stdio.h>
31285SN/A#include <stdlib.h>
32285SN/A#include <string.h>
33285SN/A
34285SN/A#include "calendar.h"
35285SN/A
36285SN/A#define	PASKHA		"paskha"
37285SN/A#define	PASKHALEN	(sizeof(PASKHA) - 1)
38285SN/A
39285SN/A/* return year day for Orthodox Easter using Gauss formula */
40285SN/A/* (old style result) */
41285SN/A
42285SN/Aint
43285SN/Apaskha(int R) /*year*/
44285SN/A{
45285SN/A	int a, b, c, d, e;
46285SN/A	static int x = 15;
47285SN/A	static int y = 6;
48285SN/A	int *cumday;
49285SN/A
50285SN/A	a = R % 19;
51285SN/A	b = R % 4;
52285SN/A	c = R % 7;
53285SN/A	d = (19 * a + x) % 30;
54285SN/A	e = (2 * b + 4 * c + 6 * d + y) % 7;
55285SN/A	cumday = cumdaytab[isleap(R)];
56285SN/A	return (((cumday[3] + 1) + 22) + (d + e));
57285SN/A}
58285SN/A