The date command in AIX doesn't support "-d" switch. So it is not easy to get the date of the days before (or after) today.

After research,I think it is best to use perl to compute the date we want.

Here it is:

#!/usr/bin/env sh
DAYS=-5
DATE=`DAYS=$DAYS perl -MPOSIX -le 'print strftime("%Y%m%d",localtime(time() + $ENV{'DAYS'} *24 *60 *60))'`

#echo $DATE