This article deals with the use or relative que with a circumstantial complement of time as an antecedent, and introducing clauses in which the relative, not preceded by a preposition, performs also in the subordinate clause the grammatical function of time adjunct. The adjunct that plays the role of an antecedent can be formed by a prepositional phrase, an adverb or a subordinate clause of time. In these cases, the relative has an adverbial function within the clause that introduces. These uses seem to continue that of undeclinable QUOD in Late Latin, which was used following a noun expressing time, to introduce a clause that indicates simultaneity. Although this type of clauses introduced by que is documented since medieval times, only when the antecedent is a time adverb or certain prepositional phrases its use is accepted in modern normative Spanish, while in other cases, specially if the antecedent is a time clause, there is a trend to reject it in the written linguistic norm, though it is still documented in colloquial speech.