The Millennial Day Theory is a literal interpretation of Bible prophecy which teaches that Jesus will return on the 6000th year since the creation of Adam. It is a popular theory among some Premillennial Fundamentalists who hold to a central belief in Young Earth Creationism.
The view takes the stance that each millennium is actually a day in God’s eyes (Psalm 90:4; 2 Peter 3:8), and that eventually during the beginning of the seventh millennium, or at the end of the 6000 years, Jesus would return. It teaches that the seventh millennium is actually called the Sabbath Millennium, in which Jesus will ultimately set up His perfect kingdom and allow His followers to rest from their works. God consistently establishes the pattern of 6 days of work and a final day of rest throughout the Bible.
Hosea 6:1-2 demonstrates that after 2 days, the Lord will heal Israel and live with her forever. Jesus has indeed been gone for 2 millenniums. He was crucified during a time of severe Roman oppression that was directed towards Israel, which eventually caused the dispersion of Israel in the first century AD. Counting the two days as two millenniums may invariably lead to the conclusion that Jesus is coming back really soon- most likely within this century. It is this perception and analysis of the prophecies that provides the motivation to create a theory that is rooted in absolute Biblical literalism and is entirely based on Dispensational Premillennialism.