A method and apparatus are provided to control artificial lighting using accurate geographical location, date and time, in order to activate such electrical activity only during needed periods of actual terrestrial darkness related to sun elevation. Accurate, real-time calculation of sun elevation relative to geographical location and date / time allow natural lighting characteristics such as natural light spectrum and intensity to be matched to artificial lighting, in order to provide a smooth transition in ambient lighting and to save energy. An apparatus according to the invention comprises a global positioning system (GPS) element for determining latitude, longitude, altitude, date and time and a calculation element for determining sun elevation angle accurately. A specific embodiment requires only desired sun elevation angle inputs from the user for controlling electrical switches in a control system.