The book of Daniel, if written by Daniel, would have been written around 550-570 BC. I believe he did write it. The later date of authorship is, I believe, an attempt to explain away the amazing accuracy of his prophecies foretelling of the Persian, Greek and Roman empires.
I concur
What makes you think he (Daniel) wrote it himself?
http://www.religioustolerance.org/daniel.htm
The text contains a number of Greek words; yet the Greek occupation of the area did not occur until the 4th century BCE.
One of the musical instruments mentioned in Daniel 3:5 and in subsequent passages did not exist until developed in 2nd century BCE Greece.
Daniel 1:4 refers to the “Chaldeans” as a priestly class in Babylon. This term did not attain this meaning until much later than the 6th century.
About 180 BCE, Jeshua ben Sira listed the heroes of the Jewish faith, including “Enoch, Noah and Abraham through to Nehemiah;” 2 Daniel is not mentioned - presumably because Jeshua is unaware of him. This would indicate that the book of Daniel was written after that time.
Chapter 12 discusses the dead being resurrected, judged, and taken to either heaven and hell. At the time of Daniel, the Jews believed that all persons went to Sheol after death. The concept of heaven and hell was introduced centuries later by the Greeks. It did not appear in Israel until the time of the Maccabean revolt.
Daniel 11:31 (and elsewhere) refers to “the abominable thing that causes desolation.” This appears to refer to the erection of a statue of Zeus in the Jerusalem temple in 167 BCE, and would indicate that the book was written later than that date.
Prior to Daniel 11:40, the author(s) has been recording past events under the Babylonian, Median, Persian and Greek empires. In Daniel 11:40-45, he really attempts to predict the future. He prophesizes that a king of the south (of the Ptolemaic dynasty) will attack the Greeks in Judea, under Antiochus. The Greeks will win, will lay spoil to all of northeast Africa, and return to Judea where Antiochus will die. The end of history will then occur. The author(s) appeared to be a poor psychic because none of these events actually happened. Antiochus did die in 164 BCE, but it was in Persia. Thus, the book was apparently completed before 164.