In order to change or edit the time on your tablet you will need to go to the Settings menu. 

To get to the Settings Menu, tap the clock twice, and select the Settings icon. ( T his is a shortcut to the Settings Menu.)
Or go to your App Launcher and select the Settings icon.

Once you have the menu open, there is a list on the left-hand side of the screen that details multiple options. Scroll down to System, and then Date & Time. 

If you are connected to Wi-Fi, you have the option to select Automatic date & time, which is provided by your network connection. If you are not connected to Wi-Fi, or the time and date are still off, then you can change the time or date by deselecting the Automatic option, and then choosing Set Time or Set Date.