Depending on where you buy your computer, you may have to set the date and time in Windows 8.1. Your computer will keep the time and date through most eventualities, so setting it once is usually more than enough.
Press Win+I to display the Settings panel of the Charms bar.
In the Settings panel, click Change PC Settings.
In the PC Settings panel, click Time & Language.
Click the Time Zone field in the right panel and then choose a time zone from the drop-down list.
If you want to, click the Adjust for Daylight Saving Time Automatically On/Off button to turn this feature on or off.
Press the Windows key on your keyboard to return to the Start screen.
Another way to display the Charms is to move your cursor to the bottom right or top right corner of the Start screen or Desktop.
If you want to set the date and time manually, you can use the Windows 8.1 Desktop Control Panel. This panel is similar to the Control Panel you may have used in previous versions of Windows. On the Start screen, click the All Apps button and begin typing the words Control Panel.
Click the Control Panel app that appears in the search results. Click Clock, Language, and Region, and then click the Set the Time and Date link to open the Date and Time dialog box and make settings.