The first serious Detailed prophecy of Daniel is Chapter 8:
The vision of the Ram with 2 horns and Goat with 1 and 4 horns.
These are explicitly identified as the Medio-Persian and Greek Empires respectively,
and it is remarkable that both the descriptions correspond closely to
the actual history of these two empires in regard to Palestine as we know them:
The correspondence is so good that skeptics have simply assumed that Daniel, or at least Daniel 8,
was actually written as late as 150 B.C.
However, the language and internal evidence is strongly against such a late date,
including various inexplicable features of Daniel, such as its division into Hebrew and Aramaic halves,
the early Persian language features, and most especially the prophecy itself:
(1) Had an 'interpolator' inserted this prophecy into the Daniel collection,
he would surely have made it correspond more closely to parts of the history
which are of deep interest to Jews in particular, and used features which
were easily confirmable as history (i.e., 'prophecy fulfilled').
(2) An 'interpolator' would not have included certain other features,
which, without convoluted explanations would seem to invalidate the prophecy:
For instance, the statement in verse 14 that the time between the ending of the
daily sacrifice and cleansing of the sanctuary would be "2,300 days (yom)",
a ridiculously long period if years were meant, and unfortunately working out to
6.3 years if taken as literal days, whereas the actual pollution of the temple
during the final days of the Greek empire seems to have been only 3-4 years,
i.e., from 167 to 164, when Judah Maccabee cleansed the temple and restored
the Mosaic Sacrfices as per normal temple practice.
These make the idea of a 'late insertion' almost untenable.
The prophecy ignores important and easily dated historical features,
such as the Rebuilding of the Temple, the Installation of Queen Esther,
the Rebuilding of the Jerusalem Wall, and the various edicts allowing
Jews to practice their religion and laws.
A prophetic forger would certainly have used at least some of these important events
as proofs of prophetic ability and for their import to Jewish interests and concerns.
The prophecy instead focuses upon Alexander, and the fact that
he dies early and his 'Empire' is divided in four among his generals.
This is an amazing prophecy, but of no concern to Jews, or even Middle Eastern affairs,
excepting insofar as one or two Ptolemic and Seleucid kings argued over
the jurisdiction of Palestine, which isn't even mentioned in the prophecy.
It strikes us that Daniel's perplexity and disturbed response to this vision
is authentic and perfectly understandable.
Daniel himself would have been concerned about Jewish issues,
as he shows in chapter 9:1-20.
The dream content and his reaction are precisely what we would expect
of a person struggling to interpret a real dream which was totally foreign to him.
There is little doubt that this prophecy in chapter 8 of Daniel
established the book as canonical prophetic work by 160 B.C.,
even if it was too late to include in 'The Prophets' section of
the Tanakh, which had already been fixed by the end of the Persian period.
As a result, Daniel, along with Esther, Ezra, and Chronicles
were relegated to 'The Writings' section fo the Tanakh,
which was still open to the inclusion of new works,
for historical purposes.