From the start, GPS has been used for accurate time keeping as well. And for later versions of the GPS protocol the week number was increased to 13 bits. https

From the start, GPS has been used for accurate time keeping as well. And for later versions of the GPS protocol the week number was increased to 13 bits. https://www.gps.gov/systems/gps/modernization/cnav/ https://www.gps.gov/systems/gps/modernization/cnav/