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The Jet Propulsion Laboratory's Deep Space Network (DSN) consists of three tracking stations located in California, Australia, and Spain, each with two hydrogen maser clocks as the time and frequency standard. Close coordination of the time and frequency of the station clocks is needed to navigate spacecraft to the outer planets. A recent example was the Voyager spacecraft's encounter with the planet Uranus in January 1986. The clocks were adjusted with the goal of minimizing the time and frequency offsets between the sites at encounter. This paper describes how the time and frequency at each complex is estimated using data acquired from Global Positioning System Timing Receivers operating on the NBS/BIH (National Bureau of Standards/Bureau International de 1'Heure) tracking schedule. These data are combined with other available timing receiver data to calculate the time offset estimates. The adjustment of the clocks is described. It was determined that the long range hydrogen maser drift is quite predictable and adjustable within limits. This enables one to minimize time and frequency differences between the three sites for many months by matching the drift rates of the three standards. The paper will describe the data acquisition and processing techniques using a Kalman filter to make estimates of time and frequency offsets between the clocks at the sites and UTC(NBS)[Coordinated Universal Time realized at NBS].