Unlike most approaches in the field of temporal expressions annotation, we consider that temporal adverbials could be relevant units from the point of view of Information Retrieval. We present here the main principles of our semantic modeling approach to temporal adverbial units. It comprises two steps: functional modeling (using a small number of basic operators) and referential modeling (using calendar intervals). In order to establish relationships between calendar zones, our approach takes into account not only the calendar values involved in adverbial units but also the semantics of prepositional phrases involved in these units. Through a first experiment, we show how Information Retrieval systems could benefit from indexing calendar expressions in texts, defining relevance scores that combine keywords and temporal ranking models.