How long was the period between Jesus's crucifixion and the destruction of the temple?
The period between Jesus's crucifixion and the Roman army's destruction of the temple was 40 years. The book of Acts covers that same 40-year span, during which God continued dealing with His covenant people while also beginning to turn to the Gentiles.
Les teaches that from the time of the crucifixion until the Roman army destroyed the temple was 40 years, and he emphasizes that the book of Acts is that same 40-year period. During it, God was still dealing with His covenant people, Israel, even though He was going to start going to the Gentiles before the 40 years were up. At the end of the 40 years, which in Israel's history was a period of testing, Israel remained adamant in unbelief. Therefore the sovereign God permitted Rome to come in, destroy the city in the most awful siege in ancient history, destroy the temple, and send Israel into dispersion among all the nations. Les notes that this dispersion has finally begun to come to an end, though it has not yet ended for the most part. Earlier in the context, he explains that Israel's repentance and baptism were the prerequisite for the King and kingdom, but God knew Israel would not do it, so He would go to the Gentiles without Israel.