Temporality is encoded in the English language through two means: tense and aspect, which are realized through lexicalization
and grammaticalization. An adequate and thorough description of temporality is fundamental for the
formalization of natural language. Temporality encoded in natural language can be analyzed into three elements: utterance time, topic time, and situation time. The relation between utterance time and topic time is entailed by tense and the relation between the topic time and the situation time is entailed by aspect. The deictic property of tense is conducive to its formalization. The present tense entails that utterance time includes topic time; the past tense entails that topic time locates before utterance time; and the future tense entails that utterance time locates before topic time. In addition, the future tense is modal in nature and it involves a possible world accessible to the present world. The tense operator is considered as a function that serves to assign each formula two parameters, the time and the world with respect to a model indexed by them the proposition is assigned a truth value. The formalization of aspect is more complicated than that of tense. On the assumption that aspect is the relation between topic time and situation time, by introducing a parameter indicating the state of
realization, the grammaticalized perfect aspect is understood to entail that topic time precedes situation time on the one hand, and the state of realization is equal with respect to both time spans on the other. The grammaticalized progressive aspect entails that topic time is properly included in situation time and that the state of realization is the same. What is termed as perfect progressive aspect in natural language combines both perfect aspect and progressive aspect in that topic time precedes situation time and that the state of realization is equal in degree with respect to the subintervals of both topic time and situation time. The concurrence of tense and aspect demands the description of both the relations between three time intervals and the relations of the state of realization with respect to topic time and situation time。