i4dy.f

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C> @file
C> @brief Convert a date-time with a 2-digit year to a date-time with
C> a 4-digit year
C>
C> @author J. Woollen @date 1998-07-08
 
C> This function converts a date-time with a 2-digit year (YYMMDDHH)
C> to a date-time with a 4-digit year (YYYYMMDDHH) using a windowing
C> technique.
C>
C> All 2-digit years greater than 40 are assumed to have a 4-digit
C> year beginning with 19 (i.e. 1941-1999), and all 2-digit years less
C> than or equal to 40 are assumed to have a 4-digit year beginning
C> with 20 (i.e. 2000-2040).  If the input date-time already contains
C> a 4-digit year, then the function simply returns that value.
C>
C> @param[in] IDATE -- integer: Date-time in format of either YYMMDDHH
C>                     (2-digit year) or YYYYMMDDHH (4-digit year)
C> @returns i4dy -- integer: Date-time in format of YYYYMMDDHH (4-digit
C>                  year)
C>
C> @author J. Woollen @date 1998-07-08
      RECURSIVE FUNCTION i4dy(IDATE) RESULT(IRET)
 
      USE modv_im8b
 
C----------------------------------------------------------------------
C----------------------------------------------------------------------
 
C     Check for I8 integers.
 
      IF(im8b) THEN
         im8b=.false.
 
         CALL x84(idate,my_idate,1)
         iret=i4dy(my_idate)
 
         im8b=.true.
         RETURN
      ENDIF
 
      IF(idate.LT.10**8) THEN
         iy = idate/10**6
         IF(iy.GT.40) THEN
            iret = idate + 19*100000000
         ELSE
            iret = idate + 20*100000000
         ENDIF
      ELSE
         iret = idate
      ENDIF
 
      RETURN
      END