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Annotation of src/usr.bin/calendar/pesach.c, Revision 1.2

1.2     ! mickey      1: /*     $OpenBSD: pesach.c,v 1.1 2004/12/10 20:47:30 mickey Exp $       */
1.1       mickey      2:
                      3: /*
                      4:  * Copyright (c) 2004 Michael Shalayeff
                      5:  * All rights reserved.
                      6:  *
                      7:  * Permission to use, copy, modify, and distribute this software for any
                      8:  * purpose with or without fee is hereby granted, provided that the above
                      9:  * copyright notice and this permission notice appear in all copies.
                     10:  *
                     11:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
                     12:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
                     13:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
                     14:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
                     15:  * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER IN
                     16:  * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
                     17:  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
                     18:  */
1.2     ! mickey     19:
        !            20: #ifndef lint
        !            21: static const char rcsid[] = "$OpenBSD$";
        !            22: #endif /* not lint */
1.1       mickey     23:
                     24: #include <stdio.h>
                     25: #include <tzfile.h>
                     26:
                     27: #include "calendar.h"
                     28:
                     29: /* Calculate the Julian date of Pesach using the Gauss formula */
                     30:
                     31: #define        T       (33. + 14. / 24.)
                     32: #define        L       ((1.  + 485. / 1080.) / 24. / 19.)
                     33: #define        K       ((29. + (12. + 793. / 1080.) / 24. ) / 19.)
                     34:
                     35: int
                     36: pesach(int R)
                     37: {
                     38:        int a, b, y, cumdays;
                     39:        double d;
                     40:
                     41:        y = R + 3760;
                     42:
                     43:        a = (12 * y + 17) % 19;
                     44:        b = y % 4;
                     45:        d = (T - 10 * K + L + 14) + K * a +  b / 4. - L * y;
                     46:        cumdays = d;
                     47:
                     48:        /* the postponement */
                     49:        switch ((int)(cumdays + 3 * y + 5 * b + 5) % 7) {
                     50:        case 1:
                     51:                if (a > 6 && d - cumdays >= (15. + 204. / 1080.) / 24.)
                     52:                        cumdays += 2;
                     53:                break;
                     54:
                     55:        case 0:
                     56:                if (a <= 11 || d - cumdays < (21. + 589. / 1080.) / 24.)
                     57:                        break;
                     58:                /* FALLTHROUGH */
                     59:        case 2:
                     60:        case 4:
                     61:        case 6:
                     62:                cumdays++;
                     63:                break;
                     64:        }
                     65:
                     66:        if (R > 1582)
                     67:                cumdays += R / 100 - R /400 - 2;
                     68:
                     69:        return (31 + 28 + cumdays + (isleap(R)? 1 : 0));
                     70: }