!$Header: /weru/cvs/weps/weps.src/util/date/caldatw.for,v 1.2 2002-09-04 20:22:17 wagner Exp $
!
!     CALDAT is taken from _Numerical_Recipes:_The_Art_of_Scientific_Computing_
!
      subroutine   caldatw (dd, mm, yyyy)

      include 'm1sim.inc'
!
!     + + + PURPOSE + + +
!     Inverse of the function JULDAY. Here 'julian' is input as a Julian Day
!     Number, and the routine outputs the dd, mm, and yyyy on which the
!     specified Julian Day started at noon.
!
!     + + + KEYWORDS + + +
!     date, utility
!
!     + + + ARGUMENT DECLARATIONS + + +
      integer   dd, mm, yyyy
      integer   igreg, julian
!
!
!     + + + ARGUMENT DEFINITIONS + + +
!     mm     - integer value of mm in the range 1-12
!     dd     -                  dd in the range 1-31
!     yyyy   -                  yyyy (negative A.D., positive B.C.)
!     julian - integer value equal to Julian Day Number
!
!     + + + PARAMETERS + + +
!     Gregorian Calendar was adopted on Oct. 15, 1582.
      parameter   (igreg=2299161)
!
!     + + + LOCAL VARIABLES + + +
      integer   jalpha, ja, jb, jc, jd, je
      real      c,e, alpha    
!
!     + + + END SPECIFICATIONS + + +
!
!     use simulation date
      julian = am0jd

      if (julian.ge.igreg) then
         alpha = (dble(julian-1867216)-dble(0.25))/dble(36524.25)
         jalpha = int(alpha)
         ja = julian+1+jalpha - int (dble(0.25)*jalpha)
      else
         ja=julian
      endif
      jb=ja+1524
      c = dble(6680.0)+((jb-2439870)-dble(122.1))/dble(365.25)
      jc = int(c)
      jd=365*jc+int (dble(0.25)*jc)
      e = (jb-jd)/dble(30.6001)
      je = int(e)
      dd=jb-jd-int (dble(30.6001)*je)
      mm=je-1
      if (mm.gt.12) mm=mm-12
      yyyy=jc-4715
      if (mm.gt.2) yyyy=yyyy-1
      if (yyyy.le.0) yyyy=yyyy-1
      return
      end
!
!$Log: not supported by cvs2svn $
!Revision 1.1  2000/03/10 21:28:36  wjr
!created new subr from caldat.  no longer passes julian arg, instead
!uses am0jd
!
!Revision 1.3  2000/01/29 22:23:24  wjr
!moved lentrim in util/misc
!combined decini & decoinit into one file, decoinit
!removed wepdgb from weps.for
!removed grad and moved calc into getcli
!moved several vars into getwin & getcli from weps
!moved *dbug.for into respective subdirs
!modified caldat to reference am0jd if arg == -1 and removed params appropriately
!
!Revision 1.2  1999/04/26 20:16:19  wagner
!changes due to combining include files ([cdb]1glob.inc), etc
!
!Revision 1.1.1.1  1999/03/12 17:05:31  wagner
!Baseline version of WEPS with Bill Rust's modifications
!
! Revision 1.1.1.1  1995/01/18  04:20:06  wagner
! Initial checkin
!
! Revision 2.3  1992/04/03  23:24:58  wagner
! Removed extraneous test print statements.
!
! Revision 2.2  1992/04/03  23:15:54  wagner
! Added some typecasts from floats to doubles (dble)
! to hopefully eliminate some roundoff error problems
! with the MS FORTRAN 5.1 compiler.
! Later, we determined that the problem was occuring
! in the julday function and not the caldat subroutine.
! However, these changes should not bother anything
! so the changes have been kept.
!
! Revision 2.1  1992/03/27  17:22:53  wagner
! Version 2 code.
!