file size older than x days

to list all file that modified more than more than X days, we can use
$ find . -mtime +[number of days]
if you use - sign than it became file is modified since X days
Combine it with akw, we can get total file size
$ find . -mtime +180 -exec du -ks {} \; | cut -f1 | awk '{total=total+$1}END{print total/1024}'