How long after the crucifixion did Jesus ascend to heaven?
Jesus was taken up from the apostles 40 days after the crucifixion. That period was the time He spoke to them before His ascension, as Peter notes when describing the qualifications for a witness of the resurrection. This timing matters because the replacement apostle had to have witnessed that entire ministry.
Les explains from Peter’s words in Acts 1 that the men gathered in the upper room had accompanied the Lord from John’s baptism until the day He was taken up. Les notes that this was 40 days after the crucifixion. The candidate to replace Judas had to be converted from John’s baptism, follow Jesus through His three years of ministry, witness the resurrection, and hear Him speak during those 40 days before the ascension. Saul of Tarsus did not qualify because he had just become a believer and had been an enemy, separated from the Twelve.