There's no how the book of Daniel will be dated less than 400BC. Why most skeptics attack this very book is not because it was written by human but for its accurate visions and prophecies being fulfilled in the past and right now.

Daniel 12:7 "And I heard the man clothed in linen, which was upon the waters of the river, when he held up his right hand and his left hand unto heaven, and sware by him that liveth for ever that it shall be for a time, times, and an half; and when he shall have accomplished to scatter the power of the holy people, all these things shall be finished."

In Daniel's vision, Daniel saw a man asking another man clothed in linen a quetsion about when the end shall come, then the man in linen cloth answered as quoted verse above.

Jesus's desciples came to Him privately, saying, tell us, when shall these things be? And what shall be the signs of thy coming, and of the of the world? Matt 24:3

Jesus begins to give the account of events of His coming and what shall before the earth and lastly, He said Matt 24:16 "And this gospel of the kingdom shall be preached in all the world for witness unto all nation; and then shall the end come."

In comparison Jesus's statement with Daniel's vision "And when he shall have accomplished to scatter the power of the Holy people 'over the world', all these things shall be finished" both give the same account of how world will end.

You have been hearing about this gospel of the true kingdom many years ago thinking Jesus is slack in His coming "Remember the power of the holy people must be scatter abroad and then end shall come".

With the fast growth in technology the "gospel of the true kingdom" has been achived more than 60%.
"Blessed is he that waiteth, and cometh to the thousand three and five and thirty days"

Are you a christain helping in spreading the "gospel of the truth" but yet your life is not in accordance with the will of God and your name is not yet in the book of life, "Remember the gospel of the kingdom shall be preached in all the world unto all nations (so that no excuse will be made) then end shall come".

Amend you ways today!

Only them that endure to the end shall be saved Matthew 24:13!