 The history of hybrid logic goes back to Arthur N. Prior’s hybrid tense logic, which is a hybridized version of ordinary tense logic. With the aim of investigating this further, we shall give a formal definition of hybrid tense logic. The language of hybrid tense logic is simply the language of hybrid logic defined above except that there are two modal operators, namely \(\mathtt{G}\) and \(\mathtt{H}\), instead of the single modal operator \(\mathtt{\Box}\). The two new modal operators are called tense operators. The semantics of hybrid tense logic is the semantics of hybrid logic, cf. earlier, with the clause for \(\mathtt{\Box}\) replaced by clauses for the tense operators \(\mathtt{G}\) and \(\mathtt{H}\).