In-game timer can be activated by going to the options menu and pressing the following keys:

• Keyboard: Ctrl+F6
• Controller: Hold right trigger, then hold left trigger, then click right stick (R3) while both triggers are held

Once successful, the timer should appear in the top-right corner of your screen. Alternatively, if you are on PC, you can use the integrated LiveSplit timer. Splits can be found here.