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File: [local] / src / usr.bin / calendar / pesach.c (download)

Revision 1.3, Tue Oct 27 23:59:36 2009 UTC (14 years, 6 months ago) by deraadt
Branch: MAIN
CVS Tags: OPENBSD_5_7_BASE, OPENBSD_5_7, OPENBSD_5_6_BASE, OPENBSD_5_6, OPENBSD_5_5_BASE, OPENBSD_5_5, OPENBSD_5_4_BASE, OPENBSD_5_4, OPENBSD_5_3_BASE, OPENBSD_5_3, OPENBSD_5_2_BASE, OPENBSD_5_2, OPENBSD_5_1_BASE, OPENBSD_5_1, OPENBSD_5_0_BASE, OPENBSD_5_0, OPENBSD_4_9_BASE, OPENBSD_4_9, OPENBSD_4_8_BASE, OPENBSD_4_8, OPENBSD_4_7_BASE, OPENBSD_4_7
Changes since 1.2: +1 -5 lines 

rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: pesach.c,v 1.3 2009/10/27 23:59:36 deraadt Exp $	*/

/*
 * Copyright (c) 2004 Michael Shalayeff
 * All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <stdio.h>
#include <tzfile.h>

#include "calendar.h"

/* Calculate the Julian date of Pesach using the Gauss formula */

#define	T	(33. + 14. / 24.)
#define	L	((1.  + 485. / 1080.) / 24. / 19.)
#define	K	((29. + (12. + 793. / 1080.) / 24. ) / 19.)

int
pesach(int R)
{
	int a, b, y, cumdays;
	double d;

	y = R + 3760;

	a = (12 * y + 17) % 19;
	b = y % 4;
	d = (T - 10 * K + L + 14) + K * a +  b / 4. - L * y;
	cumdays = d;

	/* the postponement */
	switch ((int)(cumdays + 3 * y + 5 * b + 5) % 7) {
	case 1:
		if (a > 6 && d - cumdays >= (15. + 204. / 1080.) / 24.)
			cumdays += 2;
		break;

	case 0:
		if (a <= 11 || d - cumdays < (21. + 589. / 1080.) / 24.)
			break;
		/* FALLTHROUGH */
	case 2:
	case 4:
	case 6:
		cumdays++;
		break;
	}

	if (R > 1582)
		cumdays += R / 100 - R /400 - 2;

	return (31 + 28 + cumdays + (isleap(R)? 1 : 0));
}