Was it written in the 6th or 2nd century. There appears to be evidence for both. What is the historical consensus and why? This is an extremely important question because if it was written in the 6th century it essentially proves God real
Putting aside the issue of the existence of an omnipredicate deity, you may be interested in the most recent pair of episodes of the AskHistorians Podcast, which were on the Book of Daniel. The guest, our own u/uHusky54, directly covers this question in the first part of the 1st episode. He notes that linguistic clues and contemporary evidence suggests that the Book of Daniel is not a product of the 6th C. BCE, but is Hellenistic era "vaticinium ex eventu."