Eusebius, a fourth century AD church father and considered to be the “Father of Church History,” interprets Clement of Alexandria, a second and early third century church father (cir. 155-215 AD), saying the Apostle John returned from the isle of Patmos “after the tyrant was dead”, and Eusebius identifies the “tyrant” as Domitian, Emperor of Rome from AD 81-96. He does this at the beginning of his testimony concerning John’s writing the Apocalypse. It also seems as though many modern scholars simply accept Eusebius’ testimony without even consulting Clement. If they do read Clement, it must be with the eyes of Eusebius, because Clement mentions Domitian four different times in his writings, but not once does he claim he was a tyrant or even that he persecuted Christians. Eusebius and, apparently, most modern scholarship have read this understanding into Clement’s works.
This is what Clement of Alexandria said and from which Eusebius (and modern scholarship) interpret the “tyrant” to be Domitian:
“And that you may be still more confident, that repenting thus truly there remains for you a sure hope of salvation, listen to a tale, which is not a tale but a narrative, handed down and committed to the custody of memory, about the Apostle John. For when, on the tyrant’s death, he returned to Ephesus from the isle of Patmos, he went away, being invited, to the contiguous territories of the nations, here to appoint bishops, there to set in order whole Churches, there to ordain such as were marked out by the Spirit.”
How is anyone able to conclude accurately from this statement that Domitian was the tyrant whom Clement had in mind? Therefore, Clement of Alexandria is NOT a source for John writing the Apocalypse during the reign of Domitian. Third and fourth century AD church fathers seem to base their understanding upon a single statement from Irenaeus’ works. If this is logical, it can be argued that the citation from Irenaeus is the sole foundation upon which the later church fathers base their conclusions. In other words, it is logical that although many other church fathers, living in the 3rd and 4th centuries AD, conclude that the Book of Revelation was written late in the 1st century, that their conclusions are all drawn from Irenaeus. In such a case we have only one authority—Irenaeus alone, not the other church fathers who base their understanding upon his testimony.
Moreover, the later authorities coming out of the 3rd and 4th centuries AD seem to overlook what Clement of Alexandria claimed concerning when the whole of the New Testament was written. Notice what Clement wrote:
“For the teaching of our Lord at His advent, beginning with Augustus and Tiberius, was completed in the middle of the times of Tiberius. And that of the apostles, embracing the ministry of Paul, ends with Nero”.
In other words, the writings of the Apostles (including John’s Gospel, epistles and the Apocalypse) were written between the reigns of Tiberius and Nero, so says Clement of Alexandria. Therefore, as far as “external authorities” are concerned, it comes down to whom we believe of these two: Irenaeus (as his record is usually translated) or Clement of Alexandria. Nevertheless there are other authorities that we can use in determining when the Apocalypse was written:
“In support for the early date, the Syriac version of the New Testament (dating back to the 2nd century A.D.) says the book was written during the reign of Nero. The Muratorian Fragment (170 – 190 A.D.) and the Monarchian Prologues (250 – 350 A.D.) claim that Paul wrote to seven churches following the pattern of John’s example in Revelation, placing the book of Revelation even before some of the Pauline epistles” (Expositor’s Bible Commentary, Vol. 12; p. 406).
If John wrote about things that were at hand or near, what should this say about the time John wrote the Book of Revelation? If John wrote cir. AD 95, nothing of consequence occurred shortly thereafter that the Apocalypse might be used to foretell. Nevertheless, if we are to believe the internal witness of the scriptures, the Apocalypse must have been written to alert believers of serious events that were about to occur. They were at hand (Revelation 1:3), meaning that what John wrote would come to pass shortly (Revelation 1:1; cf. Revelation 22:6, 10), and this is what all of the New Testament writers looked for (Romans 13:11; Philippians 4:5; James 5:8-9; 1Peter 4:7; 1John 2:18-19). The Apocalypse, then, if written early in the first century AD could refer only to the events leading up to the fall of Jerusalem and the destruction of the Temple, which is exactly what Jesus said would occur in this generation – his generation and that of the Apostles (Matthew 23:29-38).
 Ecclesiastical History Book 3, chapter 23.
 Clement of Alexandria; The Salvation of the Rich Man; paragraph 42
 Clement of Alexandria: The Stromata; Book 7; Chapter 17