I have viewed revalation a good many ways over the years. But the one thing that always gets me is this statement;
The revelation of Jesus Christ, which God gave him to show to his servants the things that must soon take place. He made it known by sending his angel to his servant John,
And this one;
Write therefore the things that you have seen, those that are and those that are to take place after this.
And then tie it into this one;
After this I looked, and behold, a door standing open in heaven! And the first voice, which I had heard speaking to me like a trumpet, said, "Come up here, and I will show you what must take place after this."
Three phrases - must soon take place, are to take place after this, and must take place after this.
I believe it is a continual unfolding that started with the writing of the book itself. I believe that since the time of the emergence of the last church we see described things have been unfolding ever since. When did it emerge? Who knows for sure, I have never looked real hard.
So as far as where exactly, I think somewhere mid chapter 13. I think the beast who rises from the "earth" has done so and now we will begin to see what takes place from this.
My thoughts anyways.