The article deals with the temporal adverbs as a way to express the adverbial modifier of time in the Russian and Persian languages. The concept of the functional semantic field of temporality and microfields of this field in the Russian and Persian languages is under consideration. The role of adverbs functioning as the adverbial modifier of time is highlighted. Functioning and expression of temporal adverbs are compared in the Russian and Persian languages. The authors summarize the practical experience of Russian and Iranian linguists aimed to find out the content of the adverbs of time.