This command-line tool displays a history of user accounts that were logged into the computer as well as the time and date of access from up to 2 months prior. It will even tell you the amount of time users spent logged in. I’ve had to use this method several times to catch high school students who were using their college friend’s usernames and passwords to login to our lab computers. So here’s how, its really simple..
STEPS:
1) Open Terminal.
2) Type last
and hit enter.
**If you need to pull up the login history for multiple Macs I would suggest using Apple Remote Desktop if you have it because it will display all the information at once. Just select what computers you need, click on the “Unix” tab and run the same command, preferably as root.