In the first year of Darius the son of Ahasuerus, of the seed of the Medes, which was made king over the realm of the Chaldeans;
The world-powers here recede from the view; Israel, and the salvation by Messiah promised to it, are the subject of revelation. Israel, had naturally expected salvation at the end of the captivity. Daniel is therefore told that, after the 70 years of the captivity, 70 times seven must elapse, and that even then Messiah would not come in glory, as the Jews might through misunderstanding expect from the earlier prophets, but by dying would put away sin. This ninth chapter, consisting of Messianic-prophecy, stands between the two visions of the Old Testament Antichrist, to comfort 'the wise.' In the interval between Antiochus and Christ no further revelation was needed; therefore, as in the first part of the book so in the second, Christ and Antichrist in connection are the theme.
In the first year of Darius - Cyaxares II, in whose name Cyrus, his nephew, son-in-law, and successor, took Babylon, 538 BC The date of this chapter is therefore 537 BC, a year before Cyrus permitted the Jews to return from exile, and 69 years after Daniel had been carried captive at the beginning of the captivity 606 BC
Son of Ahasuerus - called Astyages by Xenophon. Ahasuerus was a name common to many of the kings of Mode-Persia.
Made king over the realm of the Chaldeans. The phrase implies that Darius owed the kingdom, not to his own prowess, but to that of another, namely, Cyrus.