that sounds like you need atime, access time.
Just a note: Updating atime may be "expensive" in some ways (e.g. the computer may need to spin up a laptop's harddisk just to update the atime of a file that is already in the buffer cache), so there are mount options to delay or completely prevent updating the atime. For linux, search for "noatime", "strictatime", "relatime" in the mount manpage for details.
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)