ἄχρι ἧς ἡμέρας. In this construction, known as an internally headed relative clause, the head noun or antecedent (here, ἡμέρας) is actually inside the relative clause that modifies it, though it gets its case from the main clause (in this instance, the case comes from the preposition ἄχρι). A more “typical” Koine construction would have been ἄχρι ἡμέρας ἧς (cf. 1:22). The placement of the noun probably intensifies the expression: “until the very day.” ἐντειλάμενος. Aor mid dep ptc