View Your Computer Events - Through eventvwr.msc
First you should go this path
start > run >eventvwr.msc
Events are stored in three log files: Application, Security, and System.
These logs can be reviewed and archived.
For our purposes we want the System log. Click on "System" in the left-hand column for a list of events.
Look for a date and time when you weren't home and your computer should have been off.
double click on the eg: info n it will show u the detail.
You can also use this log to see how long someone was on the computer.
Just look at the time the computer was turned on and off for that day.