GPS and other satellite navigation systems give users the current time and date as well as the current position. The time derived by the satellite navigation system is very accurate, which has been used for time synchronization between network stations. By the way, the current time is represented by the limited amount of information in the navigation message of GPS and the uncertainty of week number induces 20-year period ambiguity. This paper describes some methods for determination of week number ambiguity and summarizes possible broblems regarding representation of time in GPS applications.
