[

define_tag:'lp_date_JulianDate',
	-description='Returns a Julian Date given a Gregorian date.',
	-priority='replace',
	-required='date',-copy;

	// adapted from i a u _ C A L 2 J D
	// original Fortran version follows below

	if: #date->type != 'date';
		#date = lp_date_stringtodate: (string: #date);
	/if;

	// convert to UTC/GMT
	#date = lp_date_localToUTC: #date;

	local:'d' = (integer: #date->day);
	local:'m' = (integer: #date->month);
	local:'y' = (integer: #date->year);
	local:'h' = (decimal: #date->hour);
	local:'n' = (decimal: #date->minute);
	local:'s' = (decimal: #date->second);
	
	local:'J' = integer;
	local:'MY' = integer;
	local:'IYPMY' = integer;
	local:'DJM0' = decimal;
	local:'DJM' = decimal;

            #MY = ( #m - 14 ) / 12;
            #IYPMY = #y + #MY;
            #DJM0 = 2400000.5;
            #DJM = decimal( ( 1461 * ( #IYPMY + 4800 ) ) / 4
                     + (  367 * ( #m-2 - 12*#MY ) ) / 12
                     - (    3 * ( ( #IYPMY + 4900 ) / 100 ) ) / 4
                     + #d - 2432076)
                     + (#h / 24.0) + (#n / 1440.0) + (#s / 86400.0);

	return: lp_decimal_precisionset: #DJM + #DJM0;

/define_tag;



/*

      SUBROUTINE iau_CAL2JD ( IY, IM, ID, DJM0, DJM, J )
*+
*  - - - - - - - - - - -
*   i a u _ C A L 2 J D
*  - - - - - - - - - - -
*
*  Gregorian Calendar to Julian Date.
*
*  This routine is part of the International Astronomical Union's
*  SOFA (Standards of Fundamental Astronomy) software collection.
*
*  Status:  support routine.
*
*  Given:
*     IY,IM,ID    i     year, month, day in Gregorian calendar (Note 1)
*
*  Returned:
*     DJM0        d     MJD zero-point: always 2400000.5
*     DJM         d     Modified Julian Date for 0 hrs
*     J           i     status:
*                           0 = OK
*                          -1 = bad year   (Note 3: JD not computed)
*                          -2 = bad month  (JD not computed)
*                          -3 = bad day    (JD computed)
*
*  Notes:
*
*  1) The algorithm used is valid from -4800 March 1, but this
*     implementation rejects dates before -4799 January 1.
*
*  2) The Julian Date is returned in two pieces, in the usual SOFA
*     manner, which is designed to preserve time resolution.  The
*     Julian Date is available as a single number by adding DJM0 and
*     DJM.
*
*  3) In early eras the conversion is from the "Proleptic Gregorian
*     Calendar";  no account is taken of the date(s) of adoption of
*     the Gregorian Calendar, nor is the AD/BC numbering convention
*     observed.
*
*  Reference:
*
*     Explanatory Supplement to the Astronomical Almanac,
*     P. Kenneth Seidelmann (ed), University Science Books (1992),
*     Section 12.92 (p604).
*
*  This revision:  2001 September 16
*
*  Copyright (C) 2005 IAU SOFA Review Board.  See notes at end.
*
*-----------------------------------------------------------------------

      IMPLICIT NONE

      INTEGER IY, IM, ID
      DOUBLE PRECISION DJM0, DJM
      INTEGER J, MY, IYPMY

*  Earliest year allowed (4800BC)
      INTEGER IYMIN
      PARAMETER ( IYMIN = -4799 )

*  Month lengths in days
      INTEGER MTAB(12)
      DATA MTAB / 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 /

* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

*  Preset status.
      J = 0

*  Validate year.
      IF ( IY.LT.IYMIN ) THEN
         J = -1
      ELSE

*     Validate month.
         IF ( IM.GE.1 .AND. IM.LE.12 ) THEN

*        Allow for leap year.
            IF ( MOD(IY,4) .EQ. 0 ) THEN
               MTAB(2) = 29
            ELSE
               MTAB(2) = 28
            END IF
            IF ( MOD(IY,100).EQ.0 .AND. MOD(IY,400).NE.0 ) MTAB(2) = 28

*        Validate day.
            IF ( ID.LT.1 .OR. ID.GT.MTAB(IM) ) J = -3

*        Result.
            MY = ( IM - 14 ) / 12
            IYPMY = IY + MY
            DJM0 = 2400000.5D0
            DJM = DBLE( ( 1461 * ( IYPMY + 4800 ) ) / 4
     :                + (  367 * ( IM-2 - 12*MY ) ) / 12
     :                - (    3 * ( ( IYPMY + 4900 ) / 100 ) ) / 4
     :                + ID - 2432076)

*        Bad month
         ELSE
            J = -2
         END IF
      END IF

*  Finished.

*+----------------------------------------------------------------------
*
*  Copyright (C) 2005
*  Standards Of Fundamental Astronomy Review Board
*  of the International Astronomical Union.
*
*  =====================
*  SOFA Software License
*  =====================
*
*  NOTICE TO USER:
*
*  BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING TERMS AND CONDITIONS
*  WHICH APPLY TO ITS USE.
*
*  1. The Software is owned by the IAU SOFA Review Board ("the Board").
*
*  2. The Software is made available free of charge for use by:
*
*     a) private individuals for non-profit research; and
*
*     b) non-profit educational, academic and research institutions.
*
*  3. Commercial use of the Software is specifically excluded from the
*     terms and conditions of this license.  Commercial use of the
*     Software is subject to the prior written agreement of the Board on
*     terms to be agreed.
*
*  4. The provision of any version of the Software under the terms and
*     conditions specified herein does not imply that future versions
*     will also be made available under the same terms and conditions.
*
*  5. The user may modify the Software for his/her own purposes.  The
*     user may distribute the modified software provided that the Board
*     is informed and that a copy of the modified software is made
*     available to the Board on request.  All modifications made by the
*     user shall be clearly identified to show how the modified software
*     differs from the original Software, and the name(s) of the
*     affected routine(s) shall be changed.  The original SOFA Software
*     License text must be present.
*
*  6. In any published work produced by the user and which includes
*     results achieved by using the Software, the user shall acknowledge
*     that the Software was used in producing the information contained
*     in such publication.
*
*  7. The user may incorporate or embed the Software into other software
*     products which he/she may then give away free of charge but not
*     sell provided the user makes due acknowledgement of the use which
*     he/she has made of the Software in creating such software
*     products.  Any redistribution of the Software in this way shall be
*     made under the same terms and conditions under which the user
*     received it from the SOFA Center.
*
*  8. The user shall not cause the Software to be brought into
*     disrepute, either by misuse, or use for inappropriate tasks, or by
*     inappropriate modification.
*
*  9. The Software is provided to the user "as is" and the Board makes
*     no warranty as to its use or performance.   The Board does not and
*     cannot warrant the performance or results which the user may
*     obtain by using the Software.  The Board makes no warranties,
*     express or implied, as to non-infringement of third party rights,
*     merchantability, or fitness for any particular purpose.  In no
*     event will the Board be liable to the user for any consequential,
*     incidental, or special damages, including any lost profits or lost
*     savings, even if a Board representative has been advised of such
*     damages, or for any claim by any third party.
*
*  Correspondence concerning SOFA software should be addressed as
*  follows:
*
*     Internet email: sofa@rl.ac.uk
*     Postal address: IAU SOFA Center
*                     Rutherford Appleton Laboratory
*                     Chilton, Didcot, Oxon OX11 0QX
*                     United Kingdom
*
*
*-----------------------------------------------------------------------

      END

*/

]