“Now I am come to make you understand what will befall your people in the latter days. For the vision is as yet for many days.”
The latter days are the days of the fourth empire, commencing from the time of Antiochus Epiphanes, who was outfaced by the power of Rome, and going on to the end of time. But Daniel is assured that it is many days hence. One of the main reasons for Daniel's visions was to prevent too much being made of the return from exile. Once that failed to mature into what Israel hoped for, and the hopes and expectancy were certainly there as Haggai makes clear, they would read the book of Daniel and recognise hat God had said it would be so.
‘The latter days.' The phrase first occurs in Genesis 49:1 and means in the future beyond the present time. It puts no restriction on the length of the latter days. The only point is that they are some distance away. In Numbers 22:14 it refers to the future of Moab in terms of their dealings with Israel. In Deuteronomy 31:29 it refers to the times after Moses has gone and some time has passed (compare Deuteronomy 4:30). In Daniel 2:28 it includes the subsequent empires to Nebuchadnezzar's. Thus it simply refers to the future without limitation.