When was Saul converted and when did he begin his ministry?
Saul was converted about 37 A.D. and began his ministry about 40 A.D. The context notes that around 60 A.D., some twenty years after he began ministering to the Gentiles, Paul was receiving word that Galatian congregations were being led back under the Law.
Les explains that Paul is likely writing Galatians from Corinth around 60 A.D. He estimates that Saul was converted about 37 A.D. and began his ministry about 40 A.D., so roughly twenty years after beginning his ministry to the Gentiles, Paul was getting word that the little congregations in central Turkey, which was Galatia, were being bombarded to go back under the Law. Galatians was written to correct that false teaching and bring them back under the pure grace of God.