According to this allegory, the return of Jesus and the raising of saints to meet him "in the air" in the "rapture," is Jesus returning to those who have been born again of spirit, and their meeting him "in the spirit." The "tribulation" is what these new spiritual converts, in which God has only just "begun to reign," (Rev 11:17) then go through in their lives, as they battle the "dragon" of bad habits, the "beast" of worldliness trying to tempt them back, and the "false prophet" of fear in their lives. When they have won the battle against these dark forces, then, in the language of revelation, their "Babylon" has fallen, there is great rejoicing in heaven, and they live in the "millennium," the "thousand" or perfect and holy years of living in the kingdom of heaven, when worldliness and temptation no longer assail them. They have reached the stage where although they are still in the world, they are not of the world. "1000" here does not mean the next number after 999, according to the numerology of Revelation it means "perfect and holy."
The author discusses these, and many other fascinating interpretations, in his chapter on the Book of Revelation, and the good news is that he has placed this WHOLE CHAPTER on his web site as a free sample of his book. There are many other excerpts from the book, too, but this one is the best. To go to it, click on the following link to his site, then click on the link to "summaries and two complete chapters from the book." The site is:
IN SEARCH OF THE LOVING GOD by Mark Mason