! --------------------------------------------------------------------
! PROGRAM  YYYYMMDDConversion:
!    This program uses an external subroutine Conversion() to convert
! an integer value in the form of YYYYMMDD to Year, Month and Day.
! --------------------------------------------------------------------

PROGRAM  YYYYMMDDConversion
   IMPLICIT  NONE

   INTERFACE                            ! interface block
      SUBROUTINE  Conversion(Number, Year, Month, Day)
         INTEGER, INTENT(IN)  :: Number
         INTEGER, INTENT(OUT) :: Year, Month, Day
      END SUBROUTINE  Conversion
   END INTERFACE

   INTEGER :: YYYYMMDD, Y, M, D

   DO                                   ! loop until a zero is seen
      WRITE(*,*)  "A YYYYMMDD (e.g., 19971027) please (0 to stop) -> "
      READ(*,*)   YYYYMMDD              ! read in the value
      IF (YYYYMMDD == 0)  EXIT          ! if 0, then bail out

      CALL  Conversion(YYYYMMDD, Y, M, D)    ! do conversation

      WRITE(*,*)  "Year  = ", Y         ! display results
      WRITE(*,*)  "Month = ", M
      WRITE(*,*)  "Day   = ", D
      WRITE(*,*)
   END DO
END PROGRAM  YYYYMMDDConversion

! --------------------------------------------------------------------
! SUBROUTINE  Conversion():
!    This external subroutine takes an integer input Number in the
! form of YYYYMMDD and convert it to Year, Month and Day.  
! --------------------------------------------------------------------

SUBROUTINE  Conversion(Number, Year, Month, Day)
   IMPLICIT  NONE

   INTEGER, INTENT(IN)  :: Number
   INTEGER, INTENT(OUT) :: Year, Month, Day

   Year  = Number / 10000
   Month = MOD(Number, 10000) / 100
   Day   = MOD(Number, 100)
END SUBROUTINE  Conversion