When was the book of Revelations written?
John wrote the book of Revelation to exalt Jesus Christ and to encourage Christians to remain faithful to Him. In the book, John proclaims the final victory of Jesus over sin, death, and Satan. This message was especially meaningful to believers in the late first century, who faced harsh persecution under Roman rule. Most scholars believe John wrote Revelation around 90 to 95 AD, during the reign of the Roman emperor Domitian.
Most church leaders in the second century AD—such as Irenaeus (c. 130—202), Justin Martyr (c. 100—165), and Clement of Alexandria (c. 150—215)—favored a date in the 90s AD.
Irenaeus wrote about the timing of the book of Revelation and this man also was taught by Polycarp, a disciple of Apostle John.
For that was seen no very long time since, but almost in our day, towards the end of Domitian's reign. ( 81-96 )
Your Irenaeus quote is the foundation that the 90s AD argument rests on, and it was misinterpreted by Eusebius (260-340).
Eusebius was not a fan of the book of Revelations and attributed it to "John the Elder", not the apostle.
Irenaeus is not saying that the book of Revelations was seen written in the time of Dometian, he is speaking about the apostle John.
There is also a classical church father argument for the prior AD70 argument, but more interesting is the evidence found in the book itself.
John writes of things that must "shortly come to pass" (Revelations 1) and "shortly" does not mean 2000 years.
The book is addressed to the churches of Asia Minor where John preached.
There were "seven kings: five are fallen, and one is, and the other is not yet come; and when he cometh, he must continue a short space" (Revelations 17:10).
The 5 kings who were fallen are: Julius Cesar, Augustus Cesar, Tiberius, Caligula and Claudius.
The king that "is" at the time of writing is Nero.
John is not at liberty to openly disclose Nero's name, because he wants his letter to be delivered, so he gives the Hebrew number of the name.
The number can be found by transliterating "NERON CESAR" into Hebrew letters and adding the numbers of the letters.
The king that was to "continue for a short space" is Galba, who only continued for 7 months and 7 days.
After Galba the Roman empire was wounded in the head, falling into civil war to the extent that it appeared to be dead.
Yet out of the destruction arose the Flavian dynasty (the 8th beast), beginning with Vespasian, the father of Titus.