Note 1 at Acts 20:18: Paul had originally come into Asia Minor, or what the New Testament calls Asia (see note 3 at Acts 16:6, p. 666) during the first part of his second missionary trip (see note 1 at Acts 18:22, p. ???). However, he was forbidden by the Holy Ghost to preach the word in Asia at that time (Acts 16:6) and was instead directed to Philippi in Europe (Acts 16:9-12). About two years later during this same second missionary trip, Paul ministered briefly in the synagogue in Ephesus (Acts 18:19-21).

In this instance, where Paul is addressing the leaders of the church at Ephesus, he is probably referring to his third missionary trip where he spent three years in ministry at Ephesus (Acts 20:31) which was his longest recorded stay in any one place.