If you leave your computer on for extended periods of time, it’s usually a good idea to perform a reboot now and then. Furthermore, if you’re managing multiple computers, it’s difficult to remember when each received a reboot. That’s why Windows keeps track of your total up-time and the last time your computer booted for you. Here’s how to access those pieces of information:

To find total up-time:

Step 1: Launch the task manager. You can do this in one of three ways:

Choice 1: Press Ctrl+Alt+Delete. On the screen that appears, select Start Task Manager.

Choice 2: Right click on the taskbar and select Start Task Manager.

Choice 3: Press CtrlL+Shift+Esc to launch the task manager directly.

Step 2: In this window, click on the Performance tab.

Step 3:  Your system’s up-time is displayed next to Up Time (highlighted in the above picture) in the format of Days: Hours: Minutes: Seconds

To find last boot date:

Go to Start  –> Run –> cmd

In the command prompt, run the following commands: systeminfo | find /i “Boot Time”

-or-

systeminfo | find “Time:”

-or-

systeminfo | find “System Boot Time”

Cheers,

Happy Computing 🙂

source: cnet, superuser, serverfault