When did Paul decide to travel as a missionary?

AnswerIn his Epistle to the Galatians, Paul seems quite clear about his main travels for his first twenty years as a missionary. He said that after his conversion, he travelled first to Arabia, then Damascus (bypassing Jerusalem), Jerusalem, then Syria and Cilicia, and back to Jerusalem. Paul spent 3 years in Damascus, but escaped the city when the governor under Aretas, king of the Nabateans from 9 BCE to 40 CE, had a garrison deployed to arrest him because of his Christian activities. This information gives us a first-cut estimate for the start of Paul's missionary work There is no reason at this stage to assume that the escape should have occurred near the end of the king's reign, a somewhat improbable coincidence, but if it did then Paul's conversion was around the year 36.

On the other hand, Acts of the Apostles says that Paul went first to Damascus and Jerusalem. After some short trips in Palestine, he began his "first missionary journey" to Antioch, Seleucia, Cyprus, South Galatia and back to Antioch and Jerusalem. After a series of three long missionary journeys, Acts has Paul charged and brought before Herod Agrippa, who died in 44 CE. If this is correct and if Paul had already been an apostle for over twenty years, then his conversion and decision to become a missionary would have needed to occur sometime in the early 20s of the first century, too early for the traditional history of Christianity.