text: /*
  
  -Procedure b1900_c ( Besselian Date 1900.0 )
  
  -Abstract
  
     Return the Julian Date corresponding to Besselian Date 1900.0.
  
  -Disclaimer
  
     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE
     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S.
     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE
     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE
     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS"
     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY
     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A
     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC
     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE
     SOFTWARE AND RELATED MATERIALS, HOWEVER USED.
  
     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA
     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT
     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND,
     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS,
     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE
     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY.
  
     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF
     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY
     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE
     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE.
  
  -Required_Reading
  
     None.
  
  -Keywords
  
     CONSTANTS
  
  */
  
     #include "SpiceUsr.h"
  
     SpiceDouble b1900_c ( void )
  
  /*
  
  -Brief_I/O
  
     The function returns the Julian Date corresponding to Besselian
     date 1900.0.
  
  -Detailed_Input
  
     None.
  
  -Detailed_Output
  
     The function returns 2415020.31352, the Julian Date corresponding
     to Besselian Date 1900.0 as reported by Lieske [1].
  
  -Parameters
  
     None.
  
  -Exceptions
  
     Error free.
  
  -Files
  
     None.
  
  -Particulars
  
     Lieske [1] defines a mapping from Julian Ephemeris Date
     to Besselian:
  
        BE = 1900. + (JED - 2415020.31352)/365.242198781
  
     The inverse mapping being:
  
        JED = (BE - 1900.)*365.242198781 + 2415020.31352
  
  -Examples
  
     The numerical results shown for these examples may differ across
     platforms. The results depend on the SPICE kernels used as
     input, the compiler and supporting libraries, and the machine
     specific arithmetic implementation.
  
     1) Display the double precision value for the Julian Date
        corresponding to the Besselian date 1900.0.
  
        Example code begins here.
  
  
        /.
           Program b1900_ex1
        ./
        #include <stdio.h>
        #include "SpiceUsr.h"
  
        int main( )
        {
           /.
           Display the B1900 date in 16.8 floating point format
           ./
           printf ( "B1900 date: %16.8f\n", b1900_c() );
  
           return ( 0 );
        }
  
  
        When this program was executed on a Mac/Intel/cc/64-bit
        platform, the output was:
  
  
        B1900 date: 2415020.31352000
  
  
     2) Convert an input time in UTC format to TDB seconds past the
        following reference epochs:
  
           - Besselian date 1900 and 1950; and
  
           - Julian date 1900, 1950, 2000 and 2100.
  
        Use the LSK kernel below to load the leap seconds and time
        constants required for the conversions.
  
           naif0012.tls
  
  
        Example code begins here.
  
  
        /.
           Program b1900_ex2
        ./
        #include <stdio.h>
        #include "SpiceUsr.h"
  
        int main( )
        {
           /.
           Local constants.
           ./
           #define        UTCSTR        "1991-NOV-26"
  
           /.
           Local variables.
           ./
           SpiceDouble             et;
           SpiceDouble             jed;
  
           /.
           Load the LSK file.
           ./
           furnsh_c ( "naif0012.tls" );
  
           /.
           Convert input UTC string to Ephemeris Time.
           ./
           str2et_c ( UTCSTR, &et );
           printf ( "Input ephemeris time  : %20.3f\n\n", et );
  
           /.
           Convert the Ephemeris Time to Julian ephemeris date, i.e.
           Julian date relative to TDB time scale.
           ./
           jed = unitim_c ( et, "ET", "JED" );
  
           /.
           Convert Julian Date to TDB seconds past the reference epochs
           and output the results.
           ./
           printf ( "TDB seconds past B1900: %20.3f\n",
                    ( jed - b1900_c() ) * spd_c()     );
           printf ( "TDB seconds past B1950: %20.3f\n",
                    ( jed - b1950_c() ) * spd_c()     );
           printf ( "TDB seconds past J1900: %20.3f\n",
                    ( jed - j1900_c() ) * spd_c()     );
           printf ( "TDB seconds past J1950: %20.3f\n",
                    ( jed - j1950_c() ) * spd_c()     );
           printf ( "TDB seconds past J2000: %20.3f\n",
                    ( jed - j2000_c() ) * spd_c()     );
           printf ( "TDB seconds past J2100: %20.3f\n",
                    ( jed - j2100_c() ) * spd_c()     );
  
           return ( 0 );
        }
  
  
        When this program was executed on a Mac/Intel/cc/64-bit
        platform, the output was:
  
  
        Input ephemeris time  :       -255614341.817
  
        TDB seconds past B1900:       2900118570.055
        TDB seconds past B1950:       1322272271.321
        TDB seconds past J1900:       2900145658.183
        TDB seconds past J1950:       1322265658.183
        TDB seconds past J2000:       -255614341.817
        TDB seconds past J2100:      -3411374341.817
  
  
  -Restrictions
  
     None.
  
  -Literature_References
  
     [1]  J. Lieske, "Precession Matrix Based on IAU (1976) System of
          Astronomical Constants," Astron. Astrophys. 73, 282-284,
          1979.
  
  -Author_and_Institution
  
     J. Diaz del Rio     (ODC Space)
     W.L. Taber          (JPL)
     I.M. Underwood      (JPL)
     E.D. Wright         (JPL)
  
  -Version
  
     -CSPICE Version 1.1.1, 06-JUL-2021 (JDR)
  
         Edited the header to comply with NAIF standard. Added
         complete code examples.
  
     -CSPICE Version 1.1.0, 01-SEP-2005 (EDW)
  
         Added journal reference and associated citations.
  
     -CSPICE Version 1.0.1, 08-FEB-1998 (EDW)
  
         Corrected and clarified header entries.
  
     -CSPICE Version 1.0.0, 25-OCT-1997 (EDW) (WLT) (IMU)
  
  -Index_Entries
  
     besselian date 1900.0
  
  -&
  */
  
  { /* Begin b1900_c */
  
    return 2415020.31352;
  
  } /* End b1900_c */
  