Precise timekeeping and navigation systems have a lot in common. Both are based on ultraprecise atomic clocks, on the capacity to measure and synchronise clocks, on the formation of a common reference time traced to the international standard time. These similarities are described showing how the time and frequency metrology has found its major application in the navigation systems, and how the pressing needs of navigation have promoted the research in the time metrology fields. The paper mostly focus on the clock and navigation equations, the necessary algorithms, and the definition of time scales used as reference in navigation and in timekeeping.