I find this useful when tracing the time I spent in the computer or when I opened/closed my computer. Find when you opened the lid: $ tail -n 1000 /var/log/system.log | grep "Wake reason: EC.LidOpen (User)" Replace 1000 with the number of lines you wish to backtrack system.log might have already logrotated. gunzip if the past logs are already rotated: $ ls /var/log/system.log* Example: $ gunzip /var/log/system.log.0.gz Find when you closed the lid: $ tail -n 1000 /var/log/system.log | grep "messageType = 0xE0000280" Example line: Nov 1 15:37:07 My-MacBook-Pro kernel[0]: AppleCamIn::systemWakeCall - messageType = 0xE0000280