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Annotation of src/usr.bin/calendar/paskha.c, Revision 1.7

1.7     ! millert     1: /*     $OpenBSD: paskha.c,v 1.6 2009/10/27 23:59:36 deraadt Exp $      */
1.1       millert     2:
                      3: /*
                      4:  * Copyright (C) 1993-1996 by Andrey A. Chernov, Moscow, Russia.
                      5:  * All rights reserved.
                      6:  *
                      7:  * Redistribution and use in source and binary forms, with or without
                      8:  * modification, are permitted provided that the following conditions
                      9:  * are met:
                     10:  * 1. Redistributions of source code must retain the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer.
                     12:  * 2. Redistributions in binary form must reproduce the above copyright
                     13:  *    notice, this list of conditions and the following disclaimer in the
                     14:  *    documentation and/or other materials provided with the distribution.
                     15:  *
                     16:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
                     17:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     18:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     19:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     20:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     21:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     22:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     23:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     24:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     25:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     26:  * SUCH DAMAGE.
                     27:  */
                     28:
                     29: #include <stdio.h>
1.3       deraadt    30:
                     31: #include "calendar.h"
1.1       millert    32:
                     33: /* return year day for Orthodox Easter using Gauss formula */
1.2       pjanzen    34: /* (new style result); subtract 13 for old style */
1.1       millert    35:
1.2       pjanzen    36: int
1.5       deraadt    37: paskha(int R)  /*year*/
1.1       millert    38: {
                     39:        int a, b, c, d, e;
                     40:        static int x = 15;
                     41:        static int y = 6;
1.2       pjanzen    42:        int cumdays;
1.1       millert    43:
                     44:        a = R % 19;
                     45:        b = R % 4;
                     46:        c = R % 7;
                     47:        d = (19*a + x) % 30;
                     48:        e = (2*b + 4*c + 6*d + y) % 7;
1.2       pjanzen    49:        cumdays = 31 + 28;
                     50:        if (isleap(R))
                     51:                cumdays++;
                     52:        return ((cumdays + 22) + (d + e) + 13);
1.1       millert    53: }