Cobol Program to Convert Gregorian Date to Julian Date For Any Input Year

IDENTIFICATION DIVISION.
PROGRAM-ID. MACJUL.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 A. 
          05 A1 PIC 9999.
          05 A2 PIC 99.
          05 A3 PIC 99.
01 B.
          05 B1 PIC 9999.
          05 B2 PIC 999.
01 C PIC 9 VALUE 2.
PROCEDURE DIVISION.
0001.
         DISPLAY "ENTER GREGORIAN DATE (YYYYMMDD):".
         ACCEPT A.
         IF A NOT NUMERIC OR A2 > 12 OR A3 > 31
         DISPLAY "INVALID DATE" GO 0001.
         MOVE A1 TO B1.
         COMPUTE B2 = A3.
         IF A2 = 12 ADD 30 TO B2 SUBTRACT 1 FROM A2.
         IF A2 = 11 ADD 31 TO B2 SUBTRACT 1 FROM A2.
         IF A2 = 10 ADD 30 TO B2 SUBTRACT 1 FROM A2.
         IF A2 = 9 ADD 31 TO B2 SUBTRACT 1 FROM A2.
         IF A2 = 8 ADD 31 TO B2 SUBTRACT 1 FROM A2.
         IF A2 = 7 ADD 30 TO B2 SUBTRACT 1 FROM A2.
         IF A2 = 6 ADD 31 TO B2 SUBTRACT 1 FROM A2.
         IF A2 = 5 ADD 30 TO B2 SUBTRACT 1 FROM A2.
         IF A2 = 4 ADD 31 TO B2 SUBTRACT 1 FROM A2.
         IF A2 = 3 ADD 28 TO B2 SUBTRACT 1 FROM A2
         DIVIDE A1 BY 4 GIVING A1 REMAINDER C
         IF C = 0 ADD 1 TO B2.
         IF A2 = 2 ADD 31 TO B2.
         DISPLAY " ".
         DISPLAY "JULION DATE IS(YYYYDDD):".
         DISPLAY B1 ":" B2.
         STOP RUN.