hwrf-baseline-20120103-1354/ungrib/src/ngl/w3/iw3jdn.f

   1        FUNCTION IW3JDN(IYEAR,MONTH,IDAY)
   2 C$$$   SUBPROGRAM  DOCUMENTATION  BLOCK
   3 C
   4 C SUBPROGRAM: IW3JDN         COMPUTE JULIAN DAY NUMBER
   5 C   AUTHOR: JONES,R.E.       ORG: W342       DATE: 87-03-29
   6 C
   7 C ABSTRACT: COMPUTES JULIAN DAY NUMBER FROM YEAR (4 DIGITS), MONTH,
   8 C   AND DAY. IW3JDN IS VALID FOR YEARS 1583 A.D. TO 3300 A.D.
   9 C   JULIAN DAY NUMBER CAN BE USED TO COMPUTE DAY OF WEEK, DAY OF
  10 C   YEAR, RECORD NUMBERS IN AN ARCHIVE, REPLACE DAY OF CENTURY,
  11 C   FIND THE NUMBER OF DAYS BETWEEN TWO DATES.
  12 C
  13 C PROGRAM HISTORY LOG:
  14 C   87-03-29  R.E.JONES
  15 C   89-10-25  R.E.JONES   CONVERT TO CRAY CFT77 FORTRAN
  16 C
  17 C USAGE:   II = IW3JDN(IYEAR,MONTH,IDAY)
  18 C
  19 C   INPUT VARIABLES:
  20 C     NAMES  INTERFACE DESCRIPTION OF VARIABLES AND TYPES
  21 C     ------ --------- -----------------------------------------------
  22 C     IYEAR  ARG LIST  INTEGER   YEAR           ( 4 DIGITS)
  23 C     MONTH  ARG LIST  INTEGER   MONTH OF YEAR   (1 - 12)
  24 C     IDAY   ARG LIST  INTEGER   DAY OF MONTH    (1 - 31)
  25 C
  26 C   OUTPUT VARIABLES:
  27 C     NAMES  INTERFACE DESCRIPTION OF VARIABLES AND TYPES
  28 C     ------ --------- -----------------------------------------------
  29 C     IW3JDN FUNTION   INTEGER   JULIAN DAY NUMBER
  30 C                      JAN. 1,1960 IS JULIAN DAY NUMBER 2436935
  31 C                      JAN. 1,1987 IS JULIAN DAY NUMBER 2446797
  32 C
  33 C   REMARKS: JULIAN PERIOD WAS DEVISED BY JOSEPH SCALIGER IN 1582.
  34 C     JULIAN DAY NUMBER #1 STARTED ON JAN. 1,4713 B.C. THREE MAJOR
  35 C     CHRONOLOGICAL CYCLES BEGIN ON THE SAME DAY. A 28-YEAR SOLAR
  36 C     CYCLE, A 19-YEAR LUNER CYCLE, A 15-YEAR INDICTION CYCLE, USED
  37 C     IN ANCIENT ROME TO REGULATE TAXES. IT WILL TAKE 7980 YEARS
  38 C     TO COMPLETE THE PERIOD, THE PRODUCT OF 28, 19, AND 15.
  39 C     SCALIGER NAMED THE PERIOD, DATE, AND NUMBER AFTER HIS FATHER
  40 C     JULIUS (NOT AFTER THE JULIAN CALENDAR). THIS SEEMS TO HAVE
  41 C     CAUSED A LOT OF CONFUSION IN TEXT BOOKS. SCALIGER NAME IS
  42 C     SPELLED THREE DIFFERENT WAYS. JULIAN DATE AND JULIAN DAY
  43 C     NUMBER ARE INTERCHANGED. A JULIAN DATE IS USED BY ASTRONOMERS
  44 C     TO COMPUTE ACCURATE TIME, IT HAS A FRACTION. WHEN TRUNCATED TO
  45 C     AN INTEGER IT IS CALLED AN JULIAN DAY NUMBER. THIS FUNCTION
  46 C     WAS IN A LETTER TO THE EDITOR OF THE COMMUNICATIONS OF THE ACM
  47 C     VOLUME 11 / NUMBER 10 / OCTOBER 1968. THE JULIAN DAY NUMBER
  48 C     CAN BE CONVERTED TO A YEAR, MONTH, DAY, DAY OF WEEK, DAY OF
  49 C     YEAR BY CALLING SUBROUTINE W3FS26.
  50 C
  51 C ATTRIBUTES:
  52 C   LANGUAGE: CRAY CFT77 FORTRAN
  53 C   MACHINE:  CRAY Y-MP8/864, CRAY Y-MP EL2/256
  54 C
  55 C$$$
  56 C
  57        IW3JDN  =    IDAY - 32075
  58      &            + 1461 * (IYEAR + 4800 + (MONTH - 14) / 12) / 4
  59      &            + 367 * (MONTH - 2 - (MONTH -14) / 12 * 12) / 12
  60      &            - 3 * ((IYEAR + 4900 + (MONTH - 14) / 12) / 100) / 4
  61        RETURN
  62        END