The present invention is a method and system of determining and assigning a geographic location such as a work or home location to the owner or user of a mobile device. Mobile devices such as smart phones, tablets, internet computers, and other hand held mobile devices may be preferentially targeted for delivery of advertising messages based upon the geographic location of the owner or user of the mobile device. The home or work location is determined based upon startup events associated with the mobile device as tracked by startup activations of the mobile device, beacon activations, tile activations, or any other Bluetooth or near field communication device activation, during either day time or night time hours.