You can find the time windows was last rebooted on your computer using systeminfo or wmic commands. Both the commands are explained below.
You can run the below command to find the Windows boot time.
systeminfo | findstr /C:"System Boot Time"
The above command works on Windows 7. If you are using Windows XP, then you need to run a slightly different command.
systeminfo | findstr /C:"System Up Time"
c:\>systeminfo | findstr /C:"System Boot Time" System Boot Time: 1/29/2012, 4:54:04 PM
We can find the boot time using wmic os command.
c:\>wmic os get lastBootUpTime LastBootUpTime 20120129165404.109999+330 c:\>
WMIC command shows the time up to milliseconds.