Jesus talks about several things in the Olivet Discourse. It's not all the same thing. Jesus talks about the destruction of the Temple, that happened in 70 AD, and the destruction of the Temple had nothing to do with Christ's future coming or the end of the age.
Notice the shift in what Jesus is saying in verse 36 of Matthew 24. He shifts the discussion, "But about that day..." The shift changes from talking about what will happen to Jerusalem, and the warnings about what to look out for there, to talking about His future coming in judgment. "But of that day and hour, no one knows" He says, and then goes at length to explain how this event will happen suddenly and without warning--there are no signs to look out for. It will happen when no one expects it, which is why He compares it to Noah's flood. Saying that in the same way as in Noah's time people were going about their business as usual, the flood came without any warning--in the same way, Jesus' coming will be sudden, without warning, two will be in a field and suddenly one is left, two working the mill, and one is left. Christ's return as the Judge of the quick and the dead--His glorious appearing on the Last Day i.e. His Parousia--is not something anyone can know or speculate, there are no signs preceding it.
When Jesus talks about signs, about what to look out for, He's not talking about His coming, He's talking about what will happen to Jerusalem.
Jesus' answer to the question of His disciples as to what signs will there be about His coming is that there won't be any, and that's why they--and us--need to be like the wise virgins who bring extra oil to watch through the night, that we need to be like the faithful servants who invest wisely with the money given and not squander it like the lazy servant. We need to be faithful to Jesus' call, to be doing as He told us--loving God, loving our neighbor as ourselves, being His disciples in this world. We don't know when He will return, and that's a good thing, it means that we can't become complacent thinking we can just sit on our hands and do nothing waiting for the end of the world--we are actually supposed to be living in the world as faithful servants of Christ, caring for our neighbors; that the Church is to be faithful, preaching the Gospel, administering the Sacraments, being Christ's body in the world.
There is an apocryphal story in which someone supposedly asked Martin Luther (I've read variations of this same story where it was some other person) what he would do today if he knew that the world was ending tomorrow. He said, "I would plant a tree." Again, the story is apocryphal, and some variations have someone other than Luther (it doesn't really matter here). But the point is even if the world was coming to an end tomorrow, we should be living today, and that means living for the long haul of life. Plant a tree, feed the hungry, care for the sick, visit those in prison, be concerned with your community, with the well-being of your neighbors, care about their good and their future, invest in people and in good things, because that is Christ's calling on each and every one of us. That no matter what our station in life, no matter what our vocation, we are Christians--live as a Christian whenever and wherever you are. Be a friend, be a father, be a mother, be a son, be a daughter, be a brother or a sister, be a doctor, be a lawyer, be a construction worker, be that person that says please and thank you to a random stranger that you may never meet again. Smell the roses, pet a puppy, share a glass of wine with a friend. Don't squander the gift of life which you have been given, don't squander the opportunity to be kind, loving, and to be a Christian toward others. Don't worry about tomorrow, for today has enough evil to worry about, Jesus says.
-CryptoLutheran
He said He would come back after a real AD, great tribulation, and there will be signs in the Sun, Moon, and Stars, and then we (the whole earth) will SEE Him coming in the sky with Glory. Acts 1, and Rev 1, also confirms He will visibly come from heaven. 
That is Jesus' take on His second coming.
