The question arises whether the millennium is a literal 1000 year period, or a symbolic one. Perhaps the answer could be better ascertained if we look at other prophesied time periods, ones that were already fulfilled, and see what that shows us. Off the top of my head I can think of the several below, all of them fulfilled literally; but I'm not sure how to research this and perhaps others might be able to contribute some other instances, whether literal or symbolic. Here are the instances already thought of: The dreams of Pharaoh's officials interpreted by Joseph as to occur in 3 days in Genesis 40; The 7 years of famine in Pharaoh's dreams in Genesis 41; Nebuchadnezzar’s dream about his insanity in Dan. 4; The 70 years of the Babylonian captivity as prophesied in Jeremiah 25:11-13 and 29:11; Jesus' prophesy regarding being in the tomb 3 days in Matt. 12:40, Mark 8:41, and John 2:19; The destruction of Jerusalem, occurring in the generation still living after Jesus' death and resurrection in Matthew 24:34. The question is directed to any serious student of the Bible. Note that the prophesy has to have been fulfilled already (partial fulfillment is fine), in order to evaluate whether it was literal, or symbolic.