When did God plan the ages?

God planned the ages in eternity past, before anything was ever created. The triune God came together in determining counsel and laid out the whole plan of the ages, including the coming of Jesus of Nazareth to Israel and the nation's rejection of their king.

Les teaches that Acts 2:22-23 records Peter addressing Israel about their crucifixion of Christ, saying Jesus was delivered by the determinate counsel of God. Les prefers the word "determining" and explains it as a determining council, like a cabinet meeting where minds meet. This is what the triune God did someplace way back in eternity past. They did not have to sit all afternoon, but at some time in the past, before anything was ever created, the triune God came together and laid out the whole plan of the ages. In that plan was the coming of Jesus of Nazareth to the nation of Israel and the nation's rejection of their king.

Acts 2:22

Ye men of Israel, hear these words; Jesus of Nazareth, a man approved of God among you by miracles and wonders and signs, which God did by him in the midst of you, as ye yourselves also know:

Acts 2:23

Him, being delivered by the determinate counsel and foreknowledge of God, ye have taken, and by wicked hands have crucified and slain:

When and how did the Triune God determine the plan of the ages?

The plan of the ages was determined by the Triune God in eternity past, before time began. In the Godhead's counsel, the Trinity settled it in a split second, not by lengthy debate, and in foreknowledge saw every detail of history unfold.