A motor vehicle digital display clock including a digital time display performed by fluorescent type display tubes provided in the passenger compartment of the motor vehicle, a driving means for generating time signals to be displayed on the display means, a selection switch means provided in the passenger compartment which generates a brightness signal and a brightness control circuit electrically coupled to the grid of the fluorescent type display tubes which controls the brightness of the fluorescent type display tubes by controlling the grid voltage in response to the brightness signal.