Upon a set day (taktēi hēmerāi). Locative case and the verbal adjective of tassō, to arrange, appoint, old word, here only in the N.T. Josephus (Ant. XVII. 6, 8; XIX. 8, 2) gives a full account of the occasion and the death of Herod Agrippa. It was the second day of the festival in honour of the Emperor Claudius, possibly his birthday rather than the Quinquennalia. The two accounts of Luke and Josephus supplement each other with no contradiction. Josephus does not mention the name of Blastus.
Arrayed himself in royal apparel (endusamenos esthēta basilikēn). First aorist middle (indirect) participle of endunō or enduō, common verb to put on. Literally, having put royal apparel on himself (a robe of silver tissue, Josephus says). The rays of the sun shone on this brilliant apparel and the vast crowd in the open amphitheatre became excited as Herod began to speak.
Made an oration (edēmēgorei). Imperfect active of dēmēgoreō, old verb from dēmēgoros (haranguer of the people), and that from dēmos (people) and agoreuō, to harangue or address the people. Only here in the N.T. He kept it up.