find . -mindepth 1 -type f -mtime +900 | xargs ls # check what will be deleted (older that 900 days)
# may need to be root, be careful
find /home/galaxy/galaxy-dist/database/tmp/ -mindepth 1 -type f -mtime +900 | xargs rm
# combine with directories and rm -rf @@@@@@ CAUTION ######
find /home/galaxy/galaxy-dist/database/tmp/ -mindepth 1 -type d -mtime +365 | xargs rm -rf
find /path/to/files* -mtime +100 -exec rm {} \; # delete files older than 100 days