Passage 4.15.1
ὡς δὲ τά τε ἄλλα ἐς τὸν πόλεμον ἕτοιμα ἦν αὐτοῖς καὶ τὰ ἀπὸ τῶν συμμάχων προθυμότερα ἢ προσεδόκων---καὶ γὰρ Ἀργείοις ἤδη καὶ Ἀρκάσι λαμπρῶς τὸ ἐς τοὺς Λακεδαιμονίους ἔχθος ἐξῆπτο---οὕτως ἀπέστησαν ἔτει τριακοστῷ μὲν καὶ ἐνάτῳ μετὰ Ἰθώμης ἅλωσιν, τετάρτῳ δὲ τῆς τρίτης Ὀλυμπιάδος καὶ εἰκοστῆς, ἣν Ἴκαρος Ὑπερησιεὺς ἐνίκα στάδιον· Ἀθήνῃσι δὲ οἱ κατʼ ἐνιαυτὸν ἦσαν ἤδη τότε ἄρχοντες, καὶ Ἀθηναίοις Τλησίας ἦρχεν.
When other matters necessary for war were prepared by them, and when the support from their allies proved more eager than they had expected—for the hostility against the Lacedaemonians among both the Argives and the Arcadians had already brilliantly flared up—they revolted in the thirty-ninth year after the capture of Ithome, in the fourth year of the twenty-third Olympiad, in which Icarus of Hyperesia won the stadion race. At Athens, annual archons had already been established by then, and Tlesias held office among the Athenians.