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