swe-glib/swe/src/swepdate.c
Gergely POLONKAI (W00d5t0ck) 449e26259b (split from Astrognome)Moved all SWE and SWE-GLib related files under swe-glib/
!!!WARNING!!!   The build system is not updated to reflect this! The
!!!WARNING!!!   whole point is to subtree the swe-glib/ directory,
!!!WARNING!!!   making SWE-Glib a separate project as it intended to be.
2013-09-05 11:36:43 +02:00

250 lines
9.8 KiB
C

/*****************************************************
$Header: swepdate.c,v 1.65 2003/06/14 13:02:01 alois Exp $
Placalc compatibility interface for Swiss Ephemeris.
date functions
*******************************************************/
/* Copyright (C) 1997 - 2008 Astrodienst AG, Switzerland. All rights reserved.
License conditions
------------------
This file is part of Swiss Ephemeris.
Swiss Ephemeris is distributed with NO WARRANTY OF ANY KIND. No author
or distributor accepts any responsibility for the consequences of using it,
or for whether it serves any particular purpose or works at all, unless he
or she says so in writing.
Swiss Ephemeris is made available by its authors under a dual licensing
system. The software developer, who uses any part of Swiss Ephemeris
in his or her software, must choose between one of the two license models,
which are
a) GNU public license version 2 or later
b) Swiss Ephemeris Professional License
The choice must be made before the software developer distributes software
containing parts of Swiss Ephemeris to others, and before any public
service using the developed software is activated.
If the developer choses the GNU GPL software license, he or she must fulfill
the conditions of that license, which includes the obligation to place his
or her whole software project under the GNU GPL or a compatible license.
See http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
If the developer choses the Swiss Ephemeris Professional license,
he must follow the instructions as found in http://www.astro.com/swisseph/
and purchase the Swiss Ephemeris Professional Edition from Astrodienst
and sign the corresponding license contract.
The License grants you the right to use, copy, modify and redistribute
Swiss Ephemeris, but only under certain conditions described in the License.
Among other things, the License requires that the copyright notices and
this notice be preserved on all copies.
Authors of the Swiss Ephemeris: Dieter Koch and Alois Treindl
The authors of Swiss Ephemeris have no control or influence over any of
the derived works, i.e. over software or services created by other
programmers which use Swiss Ephemeris functions.
The names of the authors or of the copyright holder (Astrodienst) must not
be used for promoting any software, product or service which uses or contains
the Swiss Ephemeris. This copyright notice is the ONLY place where the
names of the authors can legally appear, except in cases where they have
given special permission in writing.
The trademarks 'Swiss Ephemeris' and 'Swiss Ephemeris inside' may be used
for promoting such software, products or services.
*/
/*
* This file is part of the PLACALC compatibility interface for Swiss Ephemeris.
* It allows very easy porting of older Placalc application to the SwissEph.
* A user has to replace #include "placalc.h" and "housasp.h" with
* #include "swepcalc.h"
* If he has used "ourdef.h" he replaces it with "sweodef.h".
* Then he links his application with swepcalc.o and runs it against the
* Swiss Ephemeris DLL or linkable library.
*
* All calls which were present in the placalc sources are contained
* here, and either implemented directly or translated into Swiss Ephemeris
* calls.
*
*
*/
#include "swepcalc.h"
#include "swephexp.h"
/*************** julday ********************************************
* This function returns the absolute Julian day number (JD)
* for a given calendar date.
* The arguments are a calendar date: day, month, year as integers,
* hour as double with decimal fraction.
* If gregflag = 1, Gregorian calendar is assumed, gregflag = 0
* Julian calendar is assumed.
*
The Julian day number is system of numbering all days continously
within the time range of known human history. It should be familiar
for every astrological or astronomical programmer. The time variable
in astronomical theories is usually expressed in Julian days or
Julian centuries (36525 days per century) relative to some start day;
the start day is called 'the epoch'.
The Julian day number is a double representing the number of
days since JD = 0.0 on 1 Jan -4712, 12:00 noon.
Midnight has always a JD with fraction .5, because traditionally
the astronomical day started at noon. This was practical because
then there was no change of date during a night at the telescope.
From this comes also the fact the noon ephemerides were printed
before midnight ephemerides were introduced early in the 20th century.
NOTE: The Julian day number is named after the monk Julianus. It must
not be confused with the Julian calendar system, which is named after
Julius Cesar, the Roman politician who introduced this calendar.
The Julian century is named after Cesar, i.e. a century in the Julian
calendar. The 'gregorian' century has a variable length.
Be aware the we always use astronomical year numbering for the years
before Christ, not the historical year numbering.
Astronomical years are done with negative numbers, historical
years with indicators BC or BCE (before common era).
Year 0 (astronomical) = 1 BC
year -1 (astronomical) = 2 BC
etc.
Original author: Marc Pottenger, Los Angeles.
with bug fix for year < -4711 15-aug-88 by Alois Treindl
(The parameter sequence m,d,y still indicates the US origin,
be careful because the similar function date_conversion() uses
other parameter sequence and also Astrodienst relative juldate.)
References: Oliver Montenbruck, Grundlagen der Ephemeridenrechnung,
Verlag Sterne und Weltraum (1987), p.49 ff
related functions: revjul() reverse Julian day number: compute the
calendar date from a given JD
date_conversion() includes test for legal date values
and notifies errors like 32 January.
****************************************************************/
double
julday(int month, int day, int year, double hour, int gregflag)
{
double jd;
jd = swe_julday(year, month, day, hour, gregflag);
return jd;
}
/*
* monday = 0, ... sunday = 6
*/
int
day_of_week(double jd)
{
return (((int)floor(jd - 2433282 - 1.5) % 7) + 7) % 7;
}
/*************** julday ******************
get absolute julian day number (author: Marc Pottenger)
with bug fix for year < -4711 15-aug-88
*/
double
juldays(int gregflag, ADATE * adp)
{
return swe_julday(adp->year, adp->month, adp->day, adp->csec / 360000.0,
gregflag);
}
/*** revjul ******************************************************
revjul() is the inverse function to julday(), see the description
there.
Arguments are julian day number, calendar flag (0=julian, 1=gregorian)
return values are the calendar day, month, year and the hour of
the day with decimal fraction (0 .. 23.999999).
Be aware the we use astronomical year numbering for the years
before Christ, not the historical year numbering.
Astronomical years are done with negative numbers, historical
years with indicators BC or BCE (before common era).
Year 0 (astronomical) = 1 BC historical year
year -1 (astronomical) = 2 BC historical year
year -234 (astronomical) = 235 BC historical year
etc.
Original author Mark Pottenger, Los Angeles.
with bug fix for year < -4711 16-aug-88 Alois Treindl
*************************************************************************/
void
revjul(double jd, int gregflag, int *jmon, int *jday, int *jyear, double *jut)
{
swe_revjul(jd, gregflag, jyear, jmon, jday, jut);
}
/************************************* revjul *********
get calendar date from julian day #
with bug fix for year < -4711 16-aug-88
arguments are julian day #, calendar flag (0=julian, 1=gregorian)
*/
void
revjuls(double jd, int gregflag, struct adate *adp)
{
double jut;
swe_revjul(jd, gregflag, &adp->year, &adp->month, &adp->day, &jut);
adp->csec = jut * 360000.0 + 0.5;
}
/*********************************************************
$Header: swepdate.c,v 1.65 2003/06/14 13:02:01 alois Exp $
version 15-feb-89 16:30
This function converts some date+time input {d,m,y,utime}
into the Julian day number tgmt, which is an Astrodienst relative
Julian date.
The function checks that the input is a legal combination
of dates; for illegal dates like 32 January 1993 it returns ERR
but still converts the date correctly, i.e. like 1 Feb 1993.
The function is usually used to convert user input of birth data
into the Julian day number. Illegal dates should be notified to the user.
Be aware the we always use astronomical year numbering for the years
before Christ, not the historical year numbering.
Astronomical years are done with negative numbers, historical
years with indicators BC or BCE (before common era).
Year 0 (astronomical) = 1 BC historical.
year -1 (astronomical) = 2 BC
etc.
Many users of Astro programs do not know about this difference.
Return: OK or ERR (for illegal date)
*********************************************************/
int
date_conversion(int d, int m, int y, /* day, month, year */
centisec gutime, /* greenwich time in centiseconds */
char c, /* calendar g[regorian]|j[ulian]|a[stro = greg] */
double *tgmt
/* julian date relative 0.Jan.1950 12:00 gmt */
/* shift is 2433282 from absolute Julian date */
)
{
int rday, rmon, ryear;
double rut, jd;
int gregflag = SE_JUL_CAL;
if (c == 'g' || c == 'a')
gregflag = SE_GREG_CAL;
rut = gutime / 360000.0; /* hours GMT */
jd = julday(m, d, y, rut, gregflag);
revjul(jd, gregflag, &rmon, &rday, &ryear, &rut);
*tgmt = jd - JUL_OFFSET;
if (rmon == m && rday == d && ryear == y) {
return OK;
}
else {
return ERR;
}
} /* end date_conversion */