If you want to find out how long a person has been using their PlayStation 3, how long they've been playing a game or how long its been since they've last signed on, add them as your friend on the PlayStation Network. Their user profile on the PlayStation Network automatically displays this information and makes it available to anyone who knows where to look.
Turn on your PlayStation 3.
Allow a few seconds for your console to automatically log you in to the PlayStation Network. If your console does not automatically log you in, select the PlayStation Network icon from the menu and select "Sign In."
Select "Friends" from the main menu.
Highlight the icon for the user account you are trying to research. Press "X" to view the player's profile, which contains information about the game they are currently playing or the application they are currently using, as well as how long they have been using their PlayStation 3. If the user is not currently logged in, the screen will tell you how long it has been since the player used his console.