1/*-
2 * Copyright (c) 1997 Wolfgang Helbig
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
| 1/*-
2 * Copyright (c) 1997 Wolfgang Helbig
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
|
29#include "calendar.h"
30
31typedef struct date date;
32
33static int easterodn(int y);
34
35/* Compute Easter Sunday in Gregorian Calendar */
36date *
37easterg(int y, date *dt)
38{
39 int c, i, j, k, l, n;
40
41 n = y % 19;
42 c = y / 100;
43 k = (c - 17) / 25;
44 i = (c - c/4 -(c-k)/3 + 19 * n + 15) % 30;
45 i = i -(i/28) * (1 - (i/28) * (29/(i + 1)) * ((21 - n)/11));
46 j = (y + y/4 + i + 2 - c + c/4) % 7;
47 l = i - j;
48 dt->m = 3 + (l + 40) / 44;
49 dt->d = l + 28 - 31*(dt->m / 4);
50 dt->y = y;
51 return (dt);
52}
53
54/* Compute the Gregorian date of Easter Sunday in Julian Calendar */
55date *
56easterog(int y, date *dt)
57{
58
59 return (gdate(easterodn(y), dt));
60}
61
62/* Compute the Julian date of Easter Sunday in Julian Calendar */
63date *
64easteroj(int y, date * dt)
65{
66
67 return (jdate(easterodn(y), dt));
68}
69
70/* Compute the day number of Easter Sunday in Julian Calendar */
71static int
72easterodn(int y)
73{
74 /*
75 * Table for the easter limits in one metonic (19-year) cycle. 21
76 * to 31 is in March, 1 through 18 in April. Easter is the first
77 * sunday after the easter limit.
78 */
79 int mc[] = {5, 25, 13, 2, 22, 10, 30, 18, 7, 27, 15, 4,
80 24, 12, 1, 21, 9, 29, 17};
81
82 /* Offset from a weekday to next sunday */
83 int ns[] = {6, 5, 4, 3, 2, 1, 7};
84 date dt;
85 int dn;
86
87 /* Assign the easter limit of y to dt */
88 dt.d = mc[y % 19];
89
90 if (dt.d < 21)
91 dt.m = 4;
92 else
93 dt.m = 3;
94
95 dt.y = y;
96
97 /* Return the next sunday after the easter limit */
98 dn = ndaysj(&dt);
99 return (dn + ns[weekday(dn)]);
100}
| 30#include "calendar.h"
31
32typedef struct date date;
33
34static int easterodn(int y);
35
36/* Compute Easter Sunday in Gregorian Calendar */
37date *
38easterg(int y, date *dt)
39{
40 int c, i, j, k, l, n;
41
42 n = y % 19;
43 c = y / 100;
44 k = (c - 17) / 25;
45 i = (c - c/4 -(c-k)/3 + 19 * n + 15) % 30;
46 i = i -(i/28) * (1 - (i/28) * (29/(i + 1)) * ((21 - n)/11));
47 j = (y + y/4 + i + 2 - c + c/4) % 7;
48 l = i - j;
49 dt->m = 3 + (l + 40) / 44;
50 dt->d = l + 28 - 31*(dt->m / 4);
51 dt->y = y;
52 return (dt);
53}
54
55/* Compute the Gregorian date of Easter Sunday in Julian Calendar */
56date *
57easterog(int y, date *dt)
58{
59
60 return (gdate(easterodn(y), dt));
61}
62
63/* Compute the Julian date of Easter Sunday in Julian Calendar */
64date *
65easteroj(int y, date * dt)
66{
67
68 return (jdate(easterodn(y), dt));
69}
70
71/* Compute the day number of Easter Sunday in Julian Calendar */
72static int
73easterodn(int y)
74{
75 /*
76 * Table for the easter limits in one metonic (19-year) cycle. 21
77 * to 31 is in March, 1 through 18 in April. Easter is the first
78 * sunday after the easter limit.
79 */
80 int mc[] = {5, 25, 13, 2, 22, 10, 30, 18, 7, 27, 15, 4,
81 24, 12, 1, 21, 9, 29, 17};
82
83 /* Offset from a weekday to next sunday */
84 int ns[] = {6, 5, 4, 3, 2, 1, 7};
85 date dt;
86 int dn;
87
88 /* Assign the easter limit of y to dt */
89 dt.d = mc[y % 19];
90
91 if (dt.d < 21)
92 dt.m = 4;
93 else
94 dt.m = 3;
95
96 dt.y = y;
97
98 /* Return the next sunday after the easter limit */
99 dn = ndaysj(&dt);
100 return (dn + ns[weekday(dn)]);
101}
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