“Immediately after the tribulation of those days the sun will be darkened, and the moon will not give its light, and the stars will fall from heaven, and the powers of the heavens will be shaken.  Then will appear in heaven the sign of the Son of Man, and then all the tribes of the earth will mourn, and they will see the Son of Man coming on the clouds of heaven with power and great glory.  And he will send out his angels with a loud trumpet call, and they will gather his elect from the four winds, from one end of heaven to the other.In particular, the most controversial aspect of these three verses is the epic apocalyptic scale of what is being described. "Tribulation," "sun will be darkened," "moon will not give its light," "stars will fall from heaven"... Most people outside of the Jewish first century culture would see a pretty huge stretch between a city being demolished and these sorts of images being fulfilled. As a consequence, a large number of commentators include verses 29-31 in the second half of the Olivette Discourse and say that this is imagery of Jesus' eventual parousia, visitation, or coming (pick your favorite translation).
What I want to quickly do is just show how the gap is not nearly as great as one might think. There is actually quite a precedent for speaking of the destruction of cities in the Old Testament with at least this level of enthusiasm. Lets look at a few in passing:
"And on that day," declares the Lord GOD, "I will make the sun go down at noon and darken the earth in broad daylight."
The earth quakes before them; the heavens tremble. The sun and the moon are darkened, and the stars withdraw their shining.
When I blot you out, I will cover the heavens and make their stars dark; I will cover the sun with a cloud and the moon shall not give its light. All the bright lights of heaven will I make dark over you, and put darkness on your land, declares the Lord GOD.
For the stars of the heavens and their constellations will not give their light; the sun will be dark at its rising, and the moon will not shed its light.
All the host of heaven shall rot away, and the skies roll up like a scroll. All their hosts shall fall, as leaves fall from the vine, like leaves falling from the fig tree.
These are only a few examples, and I am sure there are even more occurrences like this in the Old Testament, but I think these should suffice to prove my point. My point is that none of these texts are referring to the eschaton at the end of the age when Christ returns. All of these verses are using this epic imagery to refer to God's judgment on specific cities. The passage in Joel refers to a judgment upon Israel; the passage from Ezekiel refers to a coming judgment upon the Pharaoh of Egypt; Isaiah 13:10 refers to coming destruction on Babylon; and finally, Isaiah 34:4 referred to a coming judgment upon Edom.
R.T. France, in his commentary on Matthew, points out that these last passages from Isaiah are obviously the source of the imagery which Jesus uses in Matt. 24:29-31. In particular, the fact that Jesus would use the language of a judgment upon Babylon to refer to a coming judgment upon Israel was terribly offensive. To say that Jerusalem deserved to be treated like Babylon was the epitome of judgment.
Avoiding other arguments which could be set forth for the inclusion of Matt. 24:29-31 into part one of the Olivette Discourse rather than the second half which does refer to Jesus' parousia at the end of the age, lets simply consider once again that epic imagery need not always refer to the second coming of Christ. Instead, we ought to see Jesus as using "language of cosmic collapse...to symbolize God's acts of judgment within history, with the emphasis on catastrophic political upheavals... If such language was appropriate to describe the end of Babylon or Edom under the judgment of God, why should it not equally describe God's judgment on Jerusalem's temple and the power structure it symbolized?" (R.T. France, Matthew, 2007, p. 922)