Daniel 12:4 But thou, O Daniel, shut up the words, and seal the book, even to the time of the end: many shall run to and fro, and knowledge shall be increased.
Daniel is a book of prophecy. It is a book of God telling us what He is going to do, what is going to come to pass. When Daniel finished his book God told him to seal the book till later because at that time no one was going to be able to understand what he was saying. So God had the book of Daniel written for a time in the future.
I am pretty sure we are in that time right now. The end is much nearer now than when Daniel wrote his book, over 500 years before the birth of Christ. Notice that in the time of the end many shall run to and fro so that is happening more today than ever. Then it says that knowledge shall increase. That has definitely happened in our life times.
So here is a book written before the fact about the last days. I think it deserves some careful study.