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Annotation of src/usr.bin/calendar/ostern.c, Revision 1.10

1.10    ! jsg         1: /*     $OpenBSD: ostern.c,v 1.9 2019/01/17 06:15:44 tedu Exp $ */
1.1       millert     2:
                      3: /*
                      4:  * Copyright (c) 1996 Wolfram Schneider <wosch@FreeBSD.org>. Berlin.
                      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 AND CONTRIBUTORS ``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 AUTHOR 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>
                     30: #include <time.h>
1.4       deraadt    31:
                     32: #include "calendar.h"
1.1       millert    33:
                     34: /* return year day for Easter */
                     35:
1.6       deraadt    36: int
                     37: easter(int year)       /* 0 ... abcd, NOT since 1900 */
1.1       millert    38: {
1.6       deraadt    39:        int     e_a, e_b, e_c, e_d, e_e,e_f, e_g, e_h, e_i, e_k;
                     40:        int     e_l, e_m, e_n, e_p, e_q;
1.1       millert    41:
1.6       deraadt    42:        /* silly, but it works */
                     43:        e_a = year % 19;
                     44:        e_b = year / 100;
                     45:        e_c = year % 100;
                     46:
                     47:        e_d = e_b / 4;
                     48:        e_e = e_b % 4;
                     49:        e_f = (e_b + 8) / 25;
                     50:        e_g = (e_b + 1 - e_f) / 3;
                     51:        e_h = ((19 * e_a) + 15 + e_b - (e_d + e_g)) % 30;
                     52:        e_i = e_c / 4;
                     53:        e_k = e_c % 4;
                     54:        e_l = (32 + 2 * e_e + 2 * e_i - (e_h + e_k)) % 7;
                     55:        e_m = (e_a + 11 * e_h + 22 * e_l) / 451;
                     56:        e_n = (e_h + e_l + 114 - (7 * e_m)) / 31;
                     57:        e_p = (e_h + e_l + 114 - (7 * e_m)) % 31;
                     58:        e_p = e_p + 1;
                     59:
                     60:        e_q = 31 + 28 + e_p;
                     61:        if (isleap(year))
                     62:                e_q++;
1.1       millert    63:
1.6       deraadt    64:        if (e_n == 4)
1.10    ! jsg        65:                e_q += 31;
1.1       millert    66:
                     67: #if DEBUG
1.6       deraadt    68:        printf("%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d\n",
                     69:            e_a, e_b, e_c, e_d, e_e, e_f, e_g, e_h,
                     70:            e_i, e_k, e_l, e_m, e_n, e_p, e_q);
1.1       millert    71: #endif
                     72:
1.6       deraadt    73:        return (e_q);
1.1       millert    74: }