Date Difference in Mainframe COBOL

     IDENTIFICATION DIVISION.       PROGRAM-ID. CDATEC.       DATA DIVISION.       WORKING-STORAGE SECTION.       01 YR PIC 9999.      ...

     IDENTIFICATION DIVISION.
      PROGRAM-ID. CDATEC.
      DATA DIVISION.
      WORKING-STORAGE SECTION.
      01 YR PIC 9999.
      01 YR1 PIC 9999.
      01 YR2 PIC 9999.
      01 MON PIC 99.
      01 MON1 PIC 99.
      01 MON2 PIC 99.
      01 D1  PIC 99.
     01 D2  PIC 99.
     01 QU1 PIC 99.
      01 REM1 PIC 99.
      01 REM2 PIC 99.
      01 REM3 PIC 99.
      01 T PIC 99999999.
      01 T1 PIC 99999999.
     01 T2 PIC 99999999.
      PROCEDURE DIVISION.
      MAINP.
          ACCEPT YR1.
          ACCEPT YR2.
          ACCEPT MON1.
00200000
          ACCEPT MON2.
00210000
          ACCEPT D1.
00220000
          ACCEPT D2.
00230000

00240001
          PERFORM LP-PARA VARYING YR FROM 1900 BY 1 UNTIL YR = YR1.
00270000
          PERFORM MN-PARA VARYING MON FROM 1 BY 1 UNTIL MON = MON1.
00280000

00281001
          MOVE T TO T1.
00290000
          COMPUTE T1 = T1 + D1.
00290100
          MOVE 0 TO T.
00291000

00292001
          PERFORM LP-PARA VARYING YR FROM 1900 BY 1 UNTIL YR = YR2.
00330000
          PERFORM MN-PARA VARYING MON FROM 1 BY 1 UNTIL MON = MON2.
00340000

00341001
          MOVE T TO T2.
00350000
          COMPUTE T2 = T2 + D2.
00350100
          COMPUTE T = T2 - T1.
00351000

00352001
          DISPLAY "THE DIFFERENCE BETWEEN DATES: ".
00360000
          DISPLAY D1 "/" MON1 "/" YR1 " & " D2 "/" MON2 "/" YR2 " IS
".00361000
          DISPLAY T.
00362000
          STOP RUN.
00370000

00371001
      LP-PARA.
00380000
          DIVIDE YR BY 400 GIVING QU1 REMAINDER REM1.
00381000
          DIVIDE YR BY 100 GIVING QU1 REMAINDER REM2.
00382000
          DIVIDE YR BY 4 GIVING QU1 REMAINDER REM3.
00383000
          IF  REM1 = 0 OR ( REM2 IS NOT = 0 AND REM3 = 0  ) THEN
00390000
            COMPUTE T = T + 366
00400000
          ELSE
00410000
            COMPUTE T = T + 365
00420000
          END-IF.
00430000

00431001
      MN-PARA.
00440000
          DIVIDE YR BY 400 GIVING QU1 REMAINDER REM1.
00441000
          DIVIDE YR BY 100 GIVING QU1 REMAINDER REM2.
00442000
          DIVIDE YR BY 4 GIVING QU1 REMAINDER REM3.
00443000
          IF MON = 1 OR MON = 3 OR MON = 5 OR MON = 7 OR MON = 8
00450000
          OR MON = 10 OR MON = 12 THEN
00460000
            COMPUTE T = T + 31
00470000
          ELSE IF MON = 4 OR MON = 6 OR MON = 9 OR MON = 11 THEN
00480000
            COMPUTE T = T + 30
00490000
          ELSE IF REM1 = 0 OR ( REM2 IS NOT = 0 AND REM3 = 0 ) THEN
00500000
            COMPUTE T = T + 29
00510000
          ELSE
00520000
            COMPUTE T = T + 28
00530000
          END-IF.
00540000