Some times you need to find all the files older than a particular date. You could us a number of programming languages to do the job or two simple Bash commands.
Lets say you want to find all the files in your home directory from before 2012.

touch --date "2012-01-01" /tmp/2012-01-01.txt
find /home/username -type f -not -newer /tmp/2012-01-01.txt
rm /tmp/2012-01-01.txt

That’s it.
Note: This works with the GNU find shipped with Linux.  I haven’t checked other find versions.