The other night I had to cleanup a mess in a couple of directories and doing it by date seemed to be the easiest way. I found this command and it worked like a charm:

find /path/to/files* -mtime +5 -exec rm {} \;

Basically use the find command to the files in question, the -mtime function in this example will find files older then 5 days, the last part executes the remove command on file it finds.

Note: Before running this command with the remove code, just run the find part of the command to validate that the files being found are the ones you want to remove (Measure twice cut once!).