Atime

Time of last access of a file, the information is taken from the inode, only if the filesystem doesn't have the noatime option.

$ stat -s $disk | tr ' ' '\n' | grep atime
st_atime=1130490958
$ date -r 1130490958
Fri Oct 28 11:15:58 CEST 2005
$ ls -luT disk
-rw-r--r--  1 root  wheel  33554432 Oct 28 11:15:58 2005 disk

It can be helpful reading the atime of a script to see when it was last run. Perhaps an rc script to see when a service was started/stoppped/restarted.