John informs us that he "was on the island that is called Patmos" (Revelation 1:9), a small, rocky Aegean island just west of due south from Ephesus, employed as a prison or place of exile by the Roman emperors. Most prisoners were required to work the quarries and mines on the island, but John's advanced age may have allowed him to avoid such backbreaking labor.
He writes that he was exiled there "for [because of] the word of God and for the testimony of Jesus Christ," an indication that his preaching had come to the attention of the Roman authorities, and judgment had gone against him. It is likely that John had spoken against the emperor cult (the worship of the current Roman emperor as a god, a practice that reached its height under Domitian, AD 81-96), and his exile rather than execution can only be attributed to Jesus' prophecy of John not facing martyrdom (John 21:22). The apostle perhaps remained on Patmos for less than two years, as such exiles were routinely released upon the death of the emperor who had exiled them.
Some Protestants and Catholics contend that John saw these visions on a Sunday because John writes that he "was in the Spirit on the Lord's Day" (Revelation 1:10). This is merely an unfortunate misunderstanding due to the prevalence of unscriptural Sunday worship throughout Christendom. In Greek, this phrase reads en teé Kuriakeé heeméra, literally "on the belonging-to-the-Lord day." Although it is different in construction to other instances of "the day of the Lord" in the New Testament, the meaning is the same. John is speaking not of the first day of the week, but of the time of God's judgment known throughout the Old Testament as "the day of the LORD." (Sunday, the first day of the week, was never known in the true church as "the Lord's Day," for Jesus Himself says He is "Lord of the Sabbath" (Mark 2:28), which is the seventh day.)
The apostle is giving the reader vital information about the time setting of his vision and thus the true application of the book of Revelation. Through the agency of God's Spirit, John received a vision of end-time events and related material that reveal to the church a unique understanding of the day of the Lord. Though couched in late first-century terms and allusions, Revelation is first and predominantly about the time of the end, when God through Christ will intervene in world affairs and establish His Kingdom on the earth. Most of its prophecies are only now beginning to be fulfilled or are still awaiting fulfillment in years just ahead. In a sense, the book of Revelation is as current as today's newspaper—even better, because we have it in advance!