Nevertheless, Jesus continued to tell the disciples when he would not come or appear. "If anyone tells you,`There he is, out in the desert,' do not go out; or,`Here he is, in the inner rooms,' do not believe it" (24:26). Jesus was driving home the point that his disciples should not be deceived either by world events or by people claiming to know when the "sign" of "the end" had occurred. Perhaps he was even meaning to tell them that the fall of Jerusalem and the temple were not the harbinger of "the end."<quoted text>
And this gospel of the kingdom shall be preached in all the world for a witness unto all nations; and then shall the end come.
When Jesus was asked about His return and the end of the world, He gave the verse above as part of the answer. And if you note it says as a "witness", this Gospel is circling the globe, yes it is, you can google it, check the media, and it will be the only subject spoken about soon. Yes, your verse is a witness to His return.
Now we come to verse 29, where Jesus began telling the disciples about the "sign" of his coming, which was the answer to their second question. The sun and moon would be darkened and "stars" (perhaps comets or meteorites) would fall from the sky (24:29). The solar system itself would be shaken.
Finally, Jesus gave the disciples the "sign" they were waiting for. He said: "At that time the sign of the Son of Man will appear in the sky, and all the nations of the earth will mourn. They will see the Son of Man coming on the clouds of the sky, with power and great glory" (24:30).
Basically, the "sign" of Jesus' coming, as he gave it, was his coming! There is a lesson here for us. Quite simply, there is no advance sign of Jesus' coming for us to be able to predict. He comes when he comes, and the people who are then alive will know it when it happens.
Matthew 24:36 But of that day and hour no one knows, not even the angels of heaven, but My Father only. gci.org