The fundamental question about a temporal model is "what is its underlying temporal structure?'' More specifically, what are the temporal primitives supported in the model, what temporal domains are available over these primitives, and whether the primitives are determinate or indeterminate? In this paper a simple, general framework for supporting temporal primitives (instants, intervals, sets of intervals) is presented. The framework allows seamless integration of dense and discrete temporal domains of time over a linearly ordered, unbounded point structure. The framework also provides a set-theoretic basis that allows uniform treatment of determinate and indeterminate temporal primitives.