Windows 8 automatically carries out system maintenance such as updating software, system diagnostics, security scanning but the default time set to perform them might not suit you.
There is a very easy way to schedule automatic maintenance to a time more convenient for you or manually start it.
1. Open Control Panel in category view.
2. Click or tap on System and Security.
3. Click or tap on Action Center.
4. In the Action Center, click or tap on Maintenance to show its options.
5. In  the Automatic Maintenance section you can:
A. Select the Start Maintenance option to begin the process right away.
B. Select Change Maintenance Settings to customize it. In this window you can change the daily hour when Windows runs maintenance tasks (by default it’s set at 2 AM). Optionally you can also allow Windows to wake up your computer from sleep to perform the scheduled maintenance.
2 AM is an hour when most people are sleeping and their computers are turned off. If you’ve had this setting for a while don’t worry about your system being out of date. Windows performs scheduled maintenance at the set hour if you’re not using your computer and it’s turned on of course. Otherwise it delays it until the next time the computer is not being used.