What is the last three and a half years of the tribulation like?
The final three and a half years are the period Daniel foretells from the midpoint, when the Antichrist defiles the Temple and turns on the Jews. It is a horrible time when the earth comes under the wrath of both God and Satan, and then all these things are finished.
Les explains that although the tribulation is seven years, Daniel is focusing on the last three and a half years. At the midpoint the Antichrist comes in, defiles the Temple, and turns on the Jew. That horrible period brings the earth under the wrath not only of God but also of Satan himself, and then everything shall be finished. Daniel heard and understood not, and asked what the end of these things would be; these Old Testament prophets got a glimpse of what was coming, but not the full picture, and Daniel was deeply frightened by it.