The general consensus is that the book of Revelation was written in 96AD, and that its content addresses events that are yet future during end times. This is referred to as the futurist view.
However, there is an alternative position, the Preterist view, that holds that the book of Revelation prophesies the fall of Jerusalem in 70 AD. Therefore, those who espouse this viewpoint date the writing of the book of Revelation earlier, approximately 66 AD.
I believe there exists both external evidence from other historical records as well as internal evidence within the body of Scripture that supports the futurist viewpoint.
John explains he was in exile on the island of Patmos when he wrote the book:
Revelation 1:9
I, John, your brother and fellow partaker in the tribulation and kingdom and perseverance which are in Jesus, was on the island called Patmos because of the word of God and the testimony of Jesus.
We know from a quote by the early church father Irenaeus that John was exiled to Patmos by the Roman Emperor Domitian, who reigned from 81 AD to 96 AD. Those who hold the Preterist view contend that there is enough ambiguity in this statement by Irenaeus to still make it possible to date the writing of Revelation before 70 AD. I am paraphrasing quite a bit, but the basic argument goes something like this. The Preterists claim that Irenaeus' quote could be inferred to mean that John, exiled to Patmos by Emperor Domitian, wrote the book of Revelation, rather than that John, while exiled to Patmos by Emperor Domitian, wrote the book of Revelation. The exact quote deals with something or someone that "was seen" on the island of Patmos. Futurists believe that Irenaeus' quote indicates that the Revelation vision was seen by John on Patmos, but the Preterists believe that Irenaeus' quote only indicates that John was seen on Patmos, thereby making it possible to disassociate the writing of the book of Revelation during John's exile to Patmos.
In my opinion the Preterists' argument falls apart when we go back to scripture. We don't need Irenaeus to tell us that John was on the island of Patmos when he saw and wrote the book of Revelation. John tells us himself in Revelation 1:9 that he was on Patmos when he had the Revelation, and in Revelation 1:11 and Revelation 1:19 he tells us that when he has the vision of the Revelation Jesus commands him to write down what he sees.
I believe there is a second piece of external evidence that confirms the futurist position that the book of Revelation was written in 96 AD and after the fall of Jerusalem. In Revelation 2:13 in the letter to the church of Pergamum Jesus alludes to Antipas, "My faithful witness, who was killed among you." I believe Jesus is referring to Antipas who was the Bishop of Pergamum at the end of the first century AD. The reason this is important in the dating of the writing of the book of Revelation is that Antipas was martyred by Domitian in 92 AD.
The Preterist view also points to some internal evidence to link the events depicted in the book of Revelation to the fall of Jerusalem in 70 AD. They look at the language in Revelation 1:1 "soon take place" and Revelation 1:3 "time is near" and conclude that the book of Revelation cannot address events that will occur in the distant future and must refer to something contemporary to its writing. However, this type of language is used in the writings of the Prophets to describe the Day of the Lord (
Ezekiel 30:3,
Joel 1:15,
Joel 2:1,
Joel 3:14,
Obadiah 1:15,
Zephaniah 1:7,
Zephaniah 1:14).
There are another couple of passages that I believe clarify this concept.
Habakkuk 2:3
For the vision is yet for the appointed time; It hastens toward the goal and it will not fail; Though it tarries, wait for it; For it will certainly come, it will not delay.God refers to some purpose of His that paradoxically seems will occur quickly, "hastens," and "will not delay," but also does not seem to be imminent, "tarries."
The author of Hebrews gives more insight into this verse when he quotes it.
Hebrews 10:37
For yet in a very little while, He who is coming will come, and will not delay.The author of Hebrews clarifies that the purpose of God described in Habakkuk 2:3 "yet for the appointed time" is the second coming of Jesus Christ. Indeed, we have excitedly anticipated the return of Jesus Christ for nearly 2000 years. However, if anyone because of this long interlude of time begins to doubt, beware! The return of Jesus Christ "will not fail." When He returns, His judgment will be swift and sure. In the meantime Habakkuk encourages us to wait for Him. Let us heed the words of Jesus Himself:
Matthew 24:45-46
"Who then is the faithful and wise servant, whom his master has set over his household, to give them their food at the proper time? Blessed is that servant whom his master will find so doing when he comes."