Description logics are considered as the logical infrastructure of knowledge representation on the semantic Web as well as information systems. To deal with imprecise temporal knowledge and its applications, we introduce a fuzzy temporal description logic (FTDL) in which such temporal is characterized in a classic description logic. The syntaxes and semantics of fuzzy temporal description logic are formally defined, and the forms of axioms and assertions are specified. Furthermore, we also show how FTDL is able to capture the various modeling evolution constraints in a concise way and to perform reasoning on the lack of temporal information.