A little more explanation would be much appreciated.
Sure ...
There have been several threads over the past few days posted by an individual that espouses the preterist view of end times. This view would see the words of Jesus in Matt 24 and the book of Revelation as fulfilled in 70 AD with the destruction of Jerusalem.
Since the book of Revelation itself claims that it is a book of prophecy, those who hold to the preterist view must place the date of Revelation before 70 AD or else it cannot be prophecy, but merely writing down what already happened. This supposed early date for Revelation goes against the view of the vast majority of Biblical scholarship that John wrote Revelation on the isle of Patmos around 95 AD.
One particular preterist, Kenneth Gentry, wrote his PhD thesis defending an early date for Revelation; he sets out to 'prove' that it was written in the mid to late 60s AD. His approach consists of identifying both external and internal evidence. Since his external evidence goes entirely against the vast majority of Biblical scholarship, he was forced to weigh his arguments with a huge bias toward the internal evidence.
This article examines the internal evidence that Gentry claims supports an early date and presents counter arguments to his.
Hope this helps ...