The other poster is saying that 70 AD was after the event. I believe, from my Hannegraffe readings, that 70 AD was the exact year that this happened.
One book of the bible was foretelling, the other telling what already happened.
Not exactly. They were both prophecies of future events. Jesus was prophesying two separate events here, one recorded by Luke and one by Matthew. Luke's prophecy is of the fall of Jerusalem in 70 AD, the subsequent Diaspora, and the Times of the Gentiles. It's right here:
"And when ye shall see Jerusalem compassed with armies, then know that the desolation thereof is nigh. Then let them which are in Judaea flee to the mountains; and let them which are in the midst of it depart out; and let not them that are in the countries enter thereinto. For these be the days of vengeance, that all things which are written may be fulfilled. But woe unto them that are with child, and to them that give suck, in those days! for there shall be great distress in the land, and wrath upon this people. And they shall fall by the edge of the sword, and shall be led away captive into all nations: and Jerusalem shall be trodden down of the Gentiles, until the times of the Gentiles be fulfilled." [Luke 21:20-24]
Matthew's prophecy is about an event of great tribulation that will occur after the Times of the Gentiles when the Jews are back in the land, and after they see abomination of desolation spoken of by Daniel the prophet:
"When ye therefore shall see the abomination of desolation, spoken of by Daniel the prophet, stand in the holy place, (whoso readeth, let him understand:) Then let them which be in Judaea flee into the mountains: Let him which is on the housetop not come down to take any thing out of his house: Neither let him which is in the field return back to take his clothes. And woe unto them that are with child, and to them that give suck in those days! But pray ye that your flight be not in the winter, neither on the sabbath day: For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be. " [Matthew 24:15-18]
Luke's prophecy was fulfilled in 70 AD and is still being fulfilled as we are still in the Times of the Gentiles. Matthew's prophecy of the abomination of desolation and great tribulation is still future.