In order to determine when the book of Revelation was written, we should first consider where the Apostle John was when he wrote it and why he was there. This is seen in the book of Revelation itself:
“I, John, your brother and fellow participant in the tribulation and kingdom and perseverance in Jesus, was on the island called Patmos because of the word of God and the testimony of Jesus.” Revelation 1:9 NASB
John was on the island of Patmos, a Roman penal colony. His testimony to Christ got him prison time there! He was sent during the scattered persecutions of the emperor Domitian. History tells us that Domitian was emperor from 81 A.D. until he was assassinated in 96 A.D. So it was at some point during that 15 year period that John wrote. But can we pinpoint it down even more?
An early Christian apologist, Irenaeus (130-202 A.D.), gives us insight as to when John received the revelation. At that time, Christians were attempting to determine the name of the Antichrist (Greek names associated with 666). Irenaeus thought a search was futile. He said in his book Against Heresies (about 180 A.D.) that if it were necessary we know the name, “it would have been announced by him who beheld the apocalyptic vision (i.e the Apostle John). For that was seen no very long time since, but almost in our day, towards the end of Domitian’s reign.” (See CCEL – ANF01 – Irenaeus Against Heresies, Book 5, XXX, 3)
So, it was towards the end of Domitian’s reign that John received the vision. We could surmise about 91-96 A.D. We should note that Irenaeus’ testimony is very significant and here’s why. Irenaeus was from Smyrna (one of the seven churches in Revelation) and knew the bishop of Smyrna, Polycarp. Polycarp (69-155 A.D.) was a disciple of none other than the Apostle John! So Irenaeus would have gotten information about the Apostle John directly through Polycarp!
Now, when did John actually write the book? Was it soon after he received the vision? The most credible testimony we have is from the pen of Jerome (347-420 A.D.), a historian who translated the Bible into Latin – the Vulgate. He wrote:
“In the fourteenth year then after Nero Domitian having raised a second persecution he (the Apostle John) was banished to the island of Patmos, and wrote the Apocalypse, on which Justin Martyr and Irenaeus afterwards wrote commentaries.” (See BibleHub – Lives of Illustrious Men – Chapter 9 – John)
So according to Jerome, John wrote the book while he was still on the island of Patmos – around 91-96 A.D.
What happened to John after he wrote the book of Revelation? Jerome continues,
“But Domitian having been put to death…, he (John) returned to Ephesus…founded and built churches throughout all Asia, and, worn out by old age, died in the sixty-eighth year after our Lord’s passion and was buried near the same city.” Jerome, Lives of Illustrious Men, IX.
John was released from Patmos (approx. 96 A.D.) and returned to Ephesus from where he did missionary work throughout Asia (Minor). He was in the very areas of the seven churches that received the letters of Revelation 2-3! John died 68 years after Jesus’ death, approximately 100 A.D., from old age (around 90 years old) and was buried somewhere near Ephesus.
The Scriptures and historical records have all of the disciples put to death except for one – the Apostle John.
Please note, the teachings of preterism say the date of the writing was much earlier. Preterists believe many of Revelation’s prophecies had already been fulfilled by 91-96 A.D. Preterists see things such as the Antichrist, the tribulation, and the Second Coming of Christ as history or understood as allegory. (See What is Preterism? By Got Questions)
However, Irenaeus (who knew Polycarp, who knew the Apostle John) thought many of John’s visions were yet to be fulfilled. Irenaeus, when referring to the ten kings of Revelation 13, noted that the Antichrist will (still future) come along and claim himself as the head of their kingdom. So Irenaeus not only put the Revelation around 91-96 A.D. but also still saw the rise of the Antichrist as a future event. He was definitely not a preterist. (See CCEL – ANF01 – Irenaeus Against Heresies, Book 5, XXX, 2)