FACT++  1.0
cal2jd.c
Go to the documentation of this file.
1 #include "erfa.h"
2 
3 int eraCal2jd(int iy, int im, int id, double *djm0, double *djm)
4 /*
5 ** - - - - - - - - - -
6 ** e r a C a l 2 j d
7 ** - - - - - - - - - -
8 **
9 ** Gregorian Calendar to Julian Date.
10 **
11 ** Given:
12 ** iy,im,id int year, month, day in Gregorian calendar (Note 1)
13 **
14 ** Returned:
15 ** djm0 double MJD zero-point: always 2400000.5
16 ** djm double Modified Julian Date for 0 hrs
17 **
18 ** Returned (function value):
19 ** int status:
20 ** 0 = OK
21 ** -1 = bad year (Note 3: JD not computed)
22 ** -2 = bad month (JD not computed)
23 ** -3 = bad day (JD computed)
24 **
25 ** Notes:
26 **
27 ** 1) The algorithm used is valid from -4800 March 1, but this
28 ** implementation rejects dates before -4799 January 1.
29 **
30 ** 2) The Julian Date is returned in two pieces, in the usual ERFA
31 ** manner, which is designed to preserve time resolution. The
32 ** Julian Date is available as a single number by adding djm0 and
33 ** djm.
34 **
35 ** 3) In early eras the conversion is from the "Proleptic Gregorian
36 ** Calendar"; no account is taken of the date(s) of adoption of
37 ** the Gregorian Calendar, nor is the AD/BC numbering convention
38 ** observed.
39 **
40 ** Reference:
41 **
42 ** Explanatory Supplement to the Astronomical Almanac,
43 ** P. Kenneth Seidelmann (ed), University Science Books (1992),
44 ** Section 12.92 (p604).
45 **
46 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
47 ** Derived, with permission, from the SOFA library. See notes at end of file.
48 */
49 {
50  int j, ly, my;
51  long iypmy;
52 
53 /* Earliest year allowed (4800BC) */
54  const int IYMIN = -4799;
55 
56 /* Month lengths in days */
57  static const int mtab[]
58  = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
59 
60 /* Preset status. */
61  j = 0;
62 
63 /* Validate year and month. */
64  if (iy < IYMIN) return -1;
65  if (im < 1 || im > 12) return -2;
66 
67 /* If February in a leap year, 1, otherwise 0. */
68  ly = ((im == 2) && !(iy%4) && (iy%100 || !(iy%400)));
69 
70 /* Validate day, taking into account leap years. */
71  if ( (id < 1) || (id > (mtab[im-1] + ly))) j = -3;
72 
73 /* Return result. */
74  my = (im - 14) / 12;
75  iypmy = (long) (iy + my);
76  *djm0 = ERFA_DJM0;
77  *djm = (double)((1461L * (iypmy + 4800L)) / 4L
78  + (367L * (long) (im - 2 - 12 * my)) / 12L
79  - (3L * ((iypmy + 4900L) / 100L)) / 4L
80  + (long) id - 2432076L);
81 
82 /* Return status. */
83  return j;
84 
85 }
86 /*----------------------------------------------------------------------
87 **
88 **
89 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
90 ** All rights reserved.
91 **
92 ** This library is derived, with permission, from the International
93 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
94 ** available from http://www.iausofa.org.
95 **
96 ** The ERFA version is intended to retain identical functionality to
97 ** the SOFA library, but made distinct through different function and
98 ** file names, as set out in the SOFA license conditions. The SOFA
99 ** original has a role as a reference standard for the IAU and IERS,
100 ** and consequently redistribution is permitted only in its unaltered
101 ** state. The ERFA version is not subject to this restriction and
102 ** therefore can be included in distributions which do not support the
103 ** concept of "read only" software.
104 **
105 ** Although the intent is to replicate the SOFA API (other than
106 ** replacement of prefix names) and results (with the exception of
107 ** bugs; any that are discovered will be fixed), SOFA is not
108 ** responsible for any errors found in this version of the library.
109 **
110 ** If you wish to acknowledge the SOFA heritage, please acknowledge
111 ** that you are using a library derived from SOFA, rather than SOFA
112 ** itself.
113 **
114 **
115 ** TERMS AND CONDITIONS
116 **
117 ** Redistribution and use in source and binary forms, with or without
118 ** modification, are permitted provided that the following conditions
119 ** are met:
120 **
121 ** 1 Redistributions of source code must retain the above copyright
122 ** notice, this list of conditions and the following disclaimer.
123 **
124 ** 2 Redistributions in binary form must reproduce the above copyright
125 ** notice, this list of conditions and the following disclaimer in
126 ** the documentation and/or other materials provided with the
127 ** distribution.
128 **
129 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
130 ** the International Astronomical Union nor the names of its
131 ** contributors may be used to endorse or promote products derived
132 ** from this software without specific prior written permission.
133 **
134 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
135 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
136 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
137 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
138 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
139 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
140 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
141 ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
142 ** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
143 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
144 ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
145 ** POSSIBILITY OF SUCH DAMAGE.
146 **
147 */
ERFA_DJM0
#define ERFA_DJM0
Definition: erfam.h:90
eraCal2jd
int eraCal2jd(int iy, int im, int id, double *djm0, double *djm)
Definition: cal2jd.c:3