An interesting discussion in the NICNT-Matthew commentary (R. T. France, p.103-04) concerning the phrase, "the kingdom of the heavens has drawn near." (Mt 3:2 NWT 1984-2013; Compare other translations here.):
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But John (and Jesus) do not simply echo this [prevailing Jewish] hope of God's rule coming soon. It has already arrived; literally, it "has come near." There has been extensive debate over the significance of the choice of the verb engizo [Strong's # 1448, "neared"], and of especially its perfect tense. The present tense, engizei, would have conveyed the standard eschatalogical hope, it "is coming near," but the perfect [tense] engiken [found in Mt 3:2] suggests something more actual. That which has completed the process of "coming near" is already present, not simply still on the way. There is a suggestive parallel use of the perfect tense of the same verb in [Matthew] 26:45-46, where Jesus' declaration "the time has come near" is paralleled with the statement that the Son of Man is being betrayed (present tense), while the following declaration that the betrayer "has come near" leads into the statement that "while he was still speaking" Judas arrived. This is not the language of an event still in the future but of one now in the process of happening. In Mark 1:15 the same phrase summarizing Jesus' proclamation is balanced by the declaration (also in the perfect tense) that "the time has been fulfilled," which surely makes the sense of present reality unmistakable. But even without that supplement [i.e. Mk 1:15] Matthew's phrase is clear enough, and is further supported by the language of [Matthew chapter 3] v. 10: the ax is already placed at the root of the trees. The time of God's effective sovereignty has arrived [i.e. in John's & Jesus' day], and now is the time for decisive action in response.
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The argument presented by R. T. France supports the idea that Jesus' rule began in the 1st century.
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The idea of Jesus beginning his rule after returning to heaven (or, conversely, after finishing his earthly mission as a human), would have an interesting effect on the explanation in Revelation of the four horseman.
If Jesus is pictured by the rider on the white horse (and many contend with that), but assuming he is, this would locate the 'giving of the crown to the white horse rider' in 33 C.E. The events of the rest of Revelation chapter 6 would stretch out from then until sometime in the future when the events of 6:12-17 take place.
The red horse and rider, being given a "great sword" would picture warfare over many centuries, and would include many developments in warfare, including the development of gun powder. The "black plague" (and numerous other plagues of past centuries) would be included in the description of the pale horse.
The fifth seal (6:9-11) would explain why the wait for the end stretches out. And it would parallel the description of the 144,000 in chapter seven explaining why the end had to wait. 7:1-4 would effectively add detail that was missing from 6:9-11.
The whole vision would have just as much meaning to the seven churches it was written to, as to any future churches. The 'wars, famines, and pestilences of Revelation chapter 6 would have a similar intent as those same things in Matthew 24. In Matthew 24 Jesus said that the wars, famines, plagues and earthquakes were NOT an indication that the end had arrived for the Jewish system.
Similarly, from the time Jesus begins ruling (in 33) the various wars, plagues, and famines that took place in the following centuries, would also not be an indication that Jesus' parousia had arrived, even though people (at any given time) would tend to view those things as an indication of a soon to come judgment by God.
Anyways, just postulating on the inevitable result this thread would have on the WT viewpoint.