FACT++  1.0
jd2cal.c
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1 #include "erfa.h"
2 
3 int eraJd2cal(double dj1, double dj2,
4  int *iy, int *im, int *id, double *fd)
5 /*
6 ** - - - - - - - - - -
7 ** e r a J d 2 c a l
8 ** - - - - - - - - - -
9 **
10 ** Julian Date to Gregorian year, month, day, and fraction of a day.
11 **
12 ** Given:
13 ** dj1,dj2 double Julian Date (Notes 1, 2)
14 **
15 ** Returned (arguments):
16 ** iy int year
17 ** im int month
18 ** id int day
19 ** fd double fraction of day
20 **
21 ** Returned (function value):
22 ** int status:
23 ** 0 = OK
24 ** -1 = unacceptable date (Note 3)
25 **
26 ** Notes:
27 **
28 ** 1) The earliest valid date is -68569.5 (-4900 March 1). The
29 ** largest value accepted is 1e9.
30 **
31 ** 2) The Julian Date is apportioned in any convenient way between
32 ** the arguments dj1 and dj2. For example, JD=2450123.7 could
33 ** be expressed in any of these ways, among others:
34 **
35 ** dj1 dj2
36 **
37 ** 2450123.7 0.0 (JD method)
38 ** 2451545.0 -1421.3 (J2000 method)
39 ** 2400000.5 50123.2 (MJD method)
40 ** 2450123.5 0.2 (date & time method)
41 **
42 ** 3) In early eras the conversion is from the "proleptic Gregorian
43 ** calendar"; no account is taken of the date(s) of adoption of
44 ** the Gregorian calendar, nor is the AD/BC numbering convention
45 ** observed.
46 **
47 ** Reference:
48 **
49 ** Explanatory Supplement to the Astronomical Almanac,
50 ** P. Kenneth Seidelmann (ed), University Science Books (1992),
51 ** Section 12.92 (p604).
52 **
53 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
54 ** Derived, with permission, from the SOFA library. See notes at end of file.
55 */
56 {
57 /* Minimum and maximum allowed JD */
58  const double DJMIN = -68569.5;
59  const double DJMAX = 1e9;
60 
61  long jd, l, n, i, k;
62  double dj, d1, d2, f1, f2, f, d;
63 
64 /* Verify date is acceptable. */
65  dj = dj1 + dj2;
66  if (dj < DJMIN || dj > DJMAX) return -1;
67 
68 /* Copy the date, big then small, and re-align to midnight. */
69  if (dj1 >= dj2) {
70  d1 = dj1;
71  d2 = dj2;
72  } else {
73  d1 = dj2;
74  d2 = dj1;
75  }
76  d2 -= 0.5;
77 
78 /* Separate day and fraction. */
79  f1 = fmod(d1, 1.0);
80  f2 = fmod(d2, 1.0);
81  f = fmod(f1 + f2, 1.0);
82  if (f < 0.0) f += 1.0;
83  d = floor(d1 - f1) + floor(d2 - f2) + floor(f1 + f2 - f);
84  jd = (long) floor(d) + 1L;
85 
86 /* Express day in Gregorian calendar. */
87  l = jd + 68569L;
88  n = (4L * l) / 146097L;
89  l -= (146097L * n + 3L) / 4L;
90  i = (4000L * (l + 1L)) / 1461001L;
91  l -= (1461L * i) / 4L - 31L;
92  k = (80L * l) / 2447L;
93  *id = (int) (l - (2447L * k) / 80L);
94  l = k / 11L;
95  *im = (int) (k + 2L - 12L * l);
96  *iy = (int) (100L * (n - 49L) + i + l);
97  *fd = f;
98 
99  return 0;
100 
101 }
102 /*----------------------------------------------------------------------
103 **
104 **
105 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
106 ** All rights reserved.
107 **
108 ** This library is derived, with permission, from the International
109 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
110 ** available from http://www.iausofa.org.
111 **
112 ** The ERFA version is intended to retain identical functionality to
113 ** the SOFA library, but made distinct through different function and
114 ** file names, as set out in the SOFA license conditions. The SOFA
115 ** original has a role as a reference standard for the IAU and IERS,
116 ** and consequently redistribution is permitted only in its unaltered
117 ** state. The ERFA version is not subject to this restriction and
118 ** therefore can be included in distributions which do not support the
119 ** concept of "read only" software.
120 **
121 ** Although the intent is to replicate the SOFA API (other than
122 ** replacement of prefix names) and results (with the exception of
123 ** bugs; any that are discovered will be fixed), SOFA is not
124 ** responsible for any errors found in this version of the library.
125 **
126 ** If you wish to acknowledge the SOFA heritage, please acknowledge
127 ** that you are using a library derived from SOFA, rather than SOFA
128 ** itself.
129 **
130 **
131 ** TERMS AND CONDITIONS
132 **
133 ** Redistribution and use in source and binary forms, with or without
134 ** modification, are permitted provided that the following conditions
135 ** are met:
136 **
137 ** 1 Redistributions of source code must retain the above copyright
138 ** notice, this list of conditions and the following disclaimer.
139 **
140 ** 2 Redistributions in binary form must reproduce the above copyright
141 ** notice, this list of conditions and the following disclaimer in
142 ** the documentation and/or other materials provided with the
143 ** distribution.
144 **
145 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
146 ** the International Astronomical Union nor the names of its
147 ** contributors may be used to endorse or promote products derived
148 ** from this software without specific prior written permission.
149 **
150 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
151 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
152 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
153 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
154 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
155 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
156 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
157 ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
158 ** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
159 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
160 ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
161 ** POSSIBILITY OF SUCH DAMAGE.
162 **
163 */
i
int i
Definition: db_dim_client.c:21
eraJd2cal
int eraJd2cal(double dj1, double dj2, int *iy, int *im, int *id, double *fd)
Definition: jd2cal.c:3