Abstract: Semantics and computation of temporal uncertainty in geographical information is discussed.It is argued that temporal uncertainty of geographical information basically lies in the multiple inconsistencies among the complexity of dynamical geographical phenomena,the powerness of computing machinery,and the capability of human cognition at different levels.Moreover,the holistic uncertainty of space-time uncertainty,motion uncertainty,and kinetics uncertainty is explained.Particularly,computation models of time position uncertainty,Now value endued with some progressive uncertainty semantics,outdatedness or currency evaluation of maps and spatial databases are designed.