The URL http://www.software.ibm.com/ad/va2000/va2k2mle.htm
has a brilliant idea from IBM called the Millennium Language Extensions.
In essence, you put a $Control statement that says the starting year of
your 100 year window, and in the Data Division, you add a clause to the
PIC that says the field is a date and what format.  Then the compiler and
run time library automatically expand the date to 8 characters for less
than and greater than comparisions.  I don't think it handles a sort though.

Example:

77  DATE-IN      PIC X(6) VALUE "971022".  << OCT 22, 1997 >>
77  DATE-DUE   PIC X(6) VALUE "010429".  << APR 29, 2001 >>

IF DATE-IN > DATE-DUE
      DISPLAY "YOU ARE OVER DUE, DUE ON " DATE-DUE
ELSE
      DISPLAY "NOT OVERDUE YET".

When this executes the first display will erroneously occur.


With IBM Millennium Language Extension.
$CONTROL WINDOW=1950
77  DATE-IN     PIC X(6) VALUE "971022" DATE YYMMDD.
77  DATE-DUE  PIC X(6) VALUE "010429" DATE YYMMDD.
                                                                  | new clause    |
IF DATE-IN > DATE-DUE
      DISPLAY "YOU ARE OVER DUE, DUE ON " DATE-DUE
ELSE
      DISPLAY "NOT OVERDUE YET".

When this executes, the compiler and run-time library will make 8
character dates for comparision, and correctly cause the second display
to occur.

At IBM, these extensions are available for COBOL on OS/390, VM, VSE,
and AIX, VisualAge COBOL on OS/2 and Windows NT and PL/1 on MVS,
VM and AIX.  Adding this feature to the HP compilers and run-time
libraries would make Y2K conversions so much faster and accurate for
those shops using the century window concept.

Mike Berkowitz
Guess? Inc.