If Daniel lived to see the fall of Babylonian under Belshazzar and was then already an old man, and also labored under Darius the Mede for a time and in his own book recorded this activity of his, the most reasonable time to assign for the composition or the completion of his book would be the decennium following the fall of Babylonian—538 B.C. to 528 B.C.2
Probably he [wrote the book] late in his life, which could have been about 530 B.C. or a few years later. Several Persian-derived governmental terms appear in the book. The presence of these words suggests that the book received its final polishing after Persian had become the official language of government. This would have been late in Daniel’s life.3For the biblically minded, this date of composition is easily established and on firm ground. This date is also established by the Authorship and Language of the book. And for those who are convinced of the deity of Jesus and accept his attestation of Daniel (Mat. 24:15), there is no need to speculate further.
1 Sundial on the south-wall of the monastery of Gurk, municipality Gurk, district Sankt Veit an der Glan, Carinthia, Austria. Copyright © 2006 by Johann Jaritz. This image is licensed under a Creative Commons Attribution-Share Alike 3.0 Unported license.
2 H. C. Leupold, Exposition of Daniel (Grand Rapids, MI: Baker Book House, 1949, 1969), 17.
3 Thomas Constable, Notes on Daniel (Garland, TX: Sonic Light, 2009), 2.