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93 lines
2.5 KiB
Fortran
93 lines
2.5 KiB
Fortran
SUBROUTINE sla_DJCAL (NDP, DJM, IYMDF, J)
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*+
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* - - - - - -
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* D J C A L
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* - - - - - -
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*
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* Modified Julian Date to Gregorian Calendar, expressed
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* in a form convenient for formatting messages (namely
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* rounded to a specified precision, and with the fields
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* stored in a single array)
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*
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* Given:
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* NDP i number of decimal places of days in fraction
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* DJM d modified Julian Date (JD-2400000.5)
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*
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* Returned:
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* IYMDF i(4) year, month, day, fraction in Gregorian
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* calendar
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* J i status: nonzero = out of range
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*
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* Any date after 4701BC March 1 is accepted.
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*
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* NDP should be 4 or less if internal overflows are to be avoided
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* on machines which use 32-bit integers.
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*
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* The algorithm is adapted from Hatcher 1984 (QJRAS 25, 53-55).
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*
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* Last revision: 22 July 2004
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*
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* Copyright P.T.Wallace. All rights reserved.
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*
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* License:
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (see SLA_CONDITIONS); if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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* Boston, MA 02111-1307 USA
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*
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*-
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IMPLICIT NONE
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INTEGER NDP
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DOUBLE PRECISION DJM
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INTEGER IYMDF(4),J
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INTEGER NFD
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DOUBLE PRECISION FD,DF,F,D
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INTEGER JD,N4,ND10
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* Validate.
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IF ( DJM.LE.-2395520D0 .OR. DJM.GE.1D9 ) THEN
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J = -1
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ELSE
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J = 0
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* Denominator of fraction.
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NFD = 10**MAX(NDP,0)
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FD = DBLE(NFD)
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* Round date and express in units of fraction.
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DF = ANINT(DJM*FD)
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* Separate day and fraction.
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F = MOD(DF,FD)
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IF (F.LT.0D0) F = F+FD
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D = (DF-F)/FD
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* Express day in Gregorian calendar.
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JD = NINT(D)+2400001
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N4 = 4*(JD+((2*((4*JD-17918)/146097)*3)/4+1)/2-37)
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ND10 = 10*(MOD(N4-237,1461)/4)+5
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IYMDF(1) = N4/1461-4712
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IYMDF(2) = MOD(ND10/306+2,12)+1
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IYMDF(3) = MOD(ND10,306)/10+1
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IYMDF(4) = NINT(F)
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END IF
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END
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