When did Peter become the first Pope, according to Roman Catholic tradition?

Roman Catholic doctrine teaches that the apostle Peter was the first Pope. Exactly when did this occur? I can imagine a few different options 1. When Jesus addressed Peter in Matthew: >I also say to you that you are Peter, and upon this rock I will build My church; and the gates of Hades will not overpower it. I will give you the keys of the kingdom of heaven; and whatever you bind on earth shall have been bound in heaven, and whatever you loose on earth shall have been loosed in heaven. Matthew 16:18-19 NASB 2. At the death of Christ 3. At the resurrection of Christ 4. At the reinstatement of Peter (John 21:15-17) 5. At the Ascension of Jesus 6. At Pentecost So, that is the question. At what specific time did Peter become the first Pope? (I assume that this coincides with the point at which Peter received the keys of the kingdom of heaven as well.)