how to know 3 mont's ago date?

i want to search file that is 3 month's ago according the file name..
file name is such

ATK_7B1_WIP_20041116160700.1.xml.dat
ATK_7B1_WIP_20041116160700.2.xml.dat
ATK_7B1_WIP_20041116160700.3.xml.dat
ATK_7B1_WIP_20041116160700.4.xml.dat
and the proram is like:
#!/bin/bash

is_older()
{
DATE=$(date -u "$1" +%Y-%m-%d)
TODAY=$(date -u "$(date +%Y-%m-%d) $2 $3 $4 $5" +%s)
COMPARE=$(date -u "$DATE" +%s)
test $(($TODAY - $COMPARE)) -le 0 && return 1 || return 0
}

for FILENAME in ATK_*.dat ; do
FILEDATE=$(echo $FILENAME | cut -c 13-20)
if is_older $FILEDATE -3 months ; then
echo "$FILENAME is older than 3 months."
else
echo "$FILENAME is younger than 3 months."
fi
done

but there's an error comparing in is_lder function such:
date: 0551-402 Invalid character in date/time specification
how can i solve this..please

Read "man date" carefuly. Your line

DATE=$(date -u "$1" +%Y-%m-%d)

is not correct. Put

set -xv

in the beginning of the script and

set -x

as the first command if the function is_older() and run the script again. You will see the intermediate results and can find the errors. If I were you, I would read (and study) some tutorial of the shell programming.

I thing I have solved something similar for you some time ago. Have you tried it?

Regards zlutovsky