The mode switch toggles the display. There's a display for alt voltage, time, odometer and trip odometer , fuel, and a couple others I'm not sure on. To reset trip odo hold the left button. To set time hold the left button until it starts to flash, then you use the mode button To change the number and the left button to toggle between number position(or vice versa). Just don't mess with it while you ride lol. My clock always seems to run fast, and if I recall so did my last one.