In subordinate clauses the action expressed by the aorist may be (a) contemporaneous, (b) antecedent, or (c) subsequent to that set forth by the main verb. The context alone decides in which sense the aorist is to be taken. (a)
ἐν τῷ χρόνῳ ὃν ἐπέσχε ὅσα ἐδύνατο κατενόησε
ἐμάχοντο μέχρι οἱ Ἀθηναῖοι ἀπέπλευσαν
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].