Article: The Book of Daniel (2/20)May 18, 2007
Daniel: The Canon
Critics argue against the canonicity of Daniel on two main grounds. The first is the claim that the Jews themselves did not accept Daniel as a prophetic book until long after the Old Testament canon was closed.
This argument fails to take into account the fact that although the present position of the book of Daniel in the Masoretic compilation of the Henrew Scriptures is among the ‘Writings’ (not the ‘Prophets’), this was not the original position of the book of Daniel within the Hebrew canon. Critics who use this argument assume that since Daniel is placed among the ‘Writings’ of the Masoretic compilation, it has always been there.
In doing so they display ignorance of the fact that the earlier placement of Daniel was in fact placed within the other books of prophecy as early as the LXX. In addition, it was included in the prophetic canon of the early Qumran community (from at least 100 BC onwards), and Josephus makes explicit reference to the book of Daniel as one of the prophetic works, proving that it was already recognised as such well before the 1st century:
‘Josephus, writing in c. 95 A.D., includes Daniel as one of the Prophets in his accounting of the composition of the Hebrew canon.
This is in his Contra Apion (Against the Jews) I, 38-39  and Antiquities, X, 11, 17. [Archer (1985): 7-8; Audet, 145; see also Barnes, 38-9] BTW, Josephus (Antiquities, b. xi. ch. viii. 3-8, 21, 22; xi. 3, 4) also describes an incident during the conquest of Palestine by Alexander the Great (332 B.C.; i.e., about 175 years before the commonly accepted date of 164 B.C. for the composition of Daniel) in which priests from Jerusalem met him and showed him the prophecies of Daniel concerning a Greek conquering the Persian empire. [Barnes, 54-5; Metzger, 219] “In all the sources of the first century A.D.–Matthew, Josephus, [and the] Qumran–Daniel is reckoned among the prophets.” [Koch, 123]’
David Conklin, ‘Evidences Relating to the Date of the Book of Daniel’, 2000