Darius … a Mede: See study note on Daniel 5:31.
Ahasuerus is the Hebrew version of a Persian word, translated into Greek as “Xerxes.” The father of Darius the Mede was likely a different Xerxes than Xerxes I, who ruled from 486 to 465 BC (see Esther 1:1). This vision occurred in 539 BC. Some suggest that Xerxes/Ahasuerus was an ancient throne name for Persian kings.