Disclosed are a system, apparatus, and method for estimating an absolute time. A mobile device receives a first timing signal of a terrestrial base station. The mobile device obtains a first timing offset, wherein the first timing offset is a transmit time bias between the first timing signal and an absolute Global Navigation Satellite System (GNSS) time, and the mobile device receives a maximum serving distance of the terrestrial base station. The mobile device estimates the absolute GNSS time based on the first timing signal, the first timing offset, and the maximum serving distance of the terrestrial base station.