Although Daniel 7-12 is in the first person, there is no clear claim that Daniel himself is the author. The book would have been completed after 537 BC, the last date recorded in the Daniel. The traditional view is that Daniel was written at the end of the sixth century or early in the fifth century, soon after Daniel’s death. For most in the academy, “no serious commentator” would consider an earlier date. But the later date for the book is a similar test of one’s scholarly credentials.
This is a highly contentious debate because conservatives tend to make the date of Daniel a litmus test for conservative orthodoxy. For many others Daniel is an apocalyptic re-casting of current events from the perspective of the middle of the second century B.C. For some readers Daniel is predictive prophecy made by a historical figure. The answer to this question touches on the genre of Daniel and the clear prediction of historical events leading up to the Maccabean Revolt and possibly the Roman Empire in the first century. One of the more difficult questions for studying the book of Daniel is when the book was written.
