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/*
* Copyright (c) 1986-2000, Hiram Clawson
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* Redistributions of source code must retain the above
* copyright notice, this list of conditions and the
* following disclaimer.
*
* Redistributions in binary form must reproduce the
* above copyright notice, this list of conditions and
* the following disclaimer in the documentation and/or
* other materials provided with the distribution.
*
* Neither name of The Museum of Hiram nor the names of
* its contributors may be used to endorse or promote products
* derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "astime.h" /* time structures */
/**
* caldat computes the day of the week, the day of the year
* the gregorian (or julian) calendar date and the universal
* time from the julian decimal date.
* for astronomical purposes, The Gregorian calendar reform occurred
* on 15 Oct. 1582. This is 05 Oct 1582 by the julian calendar.
* Input: a ut_instant structure pointer, where the j_date element
* has been set. ( = 0 for 01 Jan 4713 B.C. 12 HR UT )
*
* output: will set all the other elements of the structure.
* As a convienence, the function will also return the year.
*
* Reference: Astronomial formulae for calculators, meeus, p 23
* from fortran program by F. Espenak - April 1982 Page 277,
* 50 Year canon of solar eclipses: 1986-2035
*
*/
long caldat( date )
struct ut_instant * date;
{
double frac;
long jd;
long ka;
long kb;
long kc;
long kd;
long ke;
long ialp;
jd = (long) (date->j_date + 0.5); /* integer julian date */
frac = date->j_date + 0.5 - (double) jd + 1.0e-10; /* day fraction */
ka = (long) jd;
if ( jd >= 2299161L )
{
ialp = ( (double) jd - 1867216.25 ) / ( 36524.25 );
ka = jd + 1L + ialp - ( ialp >> 2 );
}
kb = ka + 1524L;
kc = ( (double) kb - 122.1 ) / 365.25;
kd = (double) kc * 365.25;
ke = (double) ( kb - kd ) / 30.6001;
date->day = kb - kd - ((long) ( (double) ke * 30.6001 ));
if ( ke > 13L )
date->month = ke - 13L;
else
date->month = ke - 1L;
if ( (date->month == 2) && (date->day > 28) )
date->day = 29;
if ( (date->month == 2) && (date->day == 29) && (ke == 3L) )
date->year = kc - 4716L;
else if ( date->month > 2 )
date->year = kc - 4716L;
else
date->year = kc - 4715L;
date->i_hour = date->d_hour = frac * 24.0; /* hour */
date->i_minute = date->d_minute =
( date->d_hour - (double) date->i_hour ) * 60.0; /* minute */
date->i_second = date->d_second =
( date->d_minute - (double) date->i_minute ) * 60.0;/* second */
date->weekday = (jd + 1L) % 7L; /* day of week */
if ( date->year == ((date->year >> 2) << 2) )
date->day_of_year =
( ( 275 * date->month ) / 9)
- ((date->month + 9) / 12)
+ date->day - 30;
else
date->day_of_year =
( ( 275 * date->month ) / 9)
- (((date->month + 9) / 12) << 1)
+ date->day - 30;
return( date->year );
}
/**
* juldat computes the julian decimal date (j_date) from
* the gregorian (or Julian) calendar date.
* for astronomical purposes, The Gregorian calendar reform occurred
* on 15 Oct. 1582. This is 05 Oct 1582 by the julian calendar.
* Input: a ut_instant structure pointer where Day, Month, Year and
* i_hour, i_minute, d_second have been set for the date
* in question.
*
* Output: the j_date and weekday elements of the structure will be set.
* Also, the return value of the function will be the j_date too.
*
* Reference: Astronomial formulae for calculators, meeus, p 23
* from fortran program by F. Espenak - April 1982 Page 276,
* 50 Year canon of solar eclipses: 1986-2035
*/
double juldat( date )
struct ut_instant * date;
{
double frac, gyr;
long iy0, im0;
long ia, ib;
long jd;
/* decimal day fraction */
frac = (( double)date->i_hour/ 24.0)
+ ((double) date->i_minute / 1440.0)
+ (date->d_second / 86400.0);
/* convert date to format YYYY.MMDDdd */
gyr = (double) date->year
+ (0.01 * (double) date->month)
+ (0.0001 * (double) date->day)
+ (0.0001 * frac) + 1.0e-9;
/* conversion factors */
if ( date->month <= 2 )
{
iy0 = date->year - 1L;
im0 = date->month + 12;
}
else
{
iy0 = date->year;
im0 = date->month;
}
ia = iy0 / 100L;
ib = 2L - ia + (ia >> 2);
/* calculate julian date */
if ( date->year < 0L )
jd = (long) ((365.25 * (double) iy0) - 0.75)
+ (long) (30.6001 * (im0 + 1L) )
+ (long) date->day + 1720994L;
else
jd = (long) (365.25 * (double) iy0)
+ (long) (30.6001 * (double) (im0 + 1L))
+ (long) date->day + 1720994L;
if ( gyr >= 1582.1015 ) /* on or after 15 October 1582 */
jd += ib;
date->j_date = (double) jd + frac + 0.5;
jd = (long) (date->j_date + 0.5);
date->weekday = (jd + 1L) % 7L;
return( date->j_date );
} /* end of double juldat( date ) */
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