1. A method for providing an electronic appointment scheduler for a vehicle, the method comprising: acquiring appointments with associated time data and geographical positions; acquiring a residual energy amount available for powering the vehicle; acquiring data on a geographical road network, including geographical positions of energy supply facilities suitable for the vehicle; generating a route plan and an energy replenishment plan with consideration of the time data and geographical positions associated with the appointments and with consideration of an available residual energy amount and an energy consumption by the vehicle on a potential travel route; calculating supplemental time periods associated with the appointments, which are derived based on the route plan and the energy replenishment plan; and generating and outputting an appointment schedule with the appointments and the supplemental time periods associated with the appointments.