Jonathan Knight (Revelation, Sheffield: Sheffield Academic Press, 1999) concludes that the book of Revelation was written "in the last decade of the first century CE at some point before the murder of Domitian in 96 CE" (page 19). He makes this conclusion for reasons that are listed below:
(1) Papias of Hierapolis (ca. 70-163 CE) knew the Apocalypse and he lived during the reign of Emperor Hadrian (117-138 CE). The evidence from Papias places the book's date in the first century CE.
(2) Justin Martyr (150 CE) and Irenaeus (ca. 185) both
were familiar with the Apocalypse of John (Die
Offenbarung des Johannes). Thus the book was already
being used by Christians prior to that time.
(3) Irenaeus writes that the book of Revelation was produced near the end of Domitian's reign (around 96 CE).
(4) Eusebius of Caesarea observes that John was sent to Patmos by Domitian (Hist. Eccl. 3.18.1).
In addition to Knight's proposal for the date of
Revelation, G.K. Beale (Revelation, Cambridge:
Paternoster Press, 1999) also thinks that Revelation
was written around 96 CE. He makes this proposal:
"Therefore, a date during the time of Nero is possible
for Revelation, but the later setting under Domitian
is more probable in the light of the evidence in the
book for an expected escalation of emperor worship in
the near future and especially the widespread,
programmatic legal persecution portrayed as imminent
or already occurring in Revelation 13, though the
letters reveal only spasmodic persecution" (page 9).
All in all, while there may be some debate about
when Revelation was written, I think a good case can
be made for the 96 CE date.