"But of that day and hour no one knows, not even the angels of heaven, nor the Son, but the Father alone." (Matt. 24:36; Mk. 13:32).

Notice the words "that day and hour". There was a specific day and hour when Christ would return and the old (testament) heavens & earth would pass away. Jesus did not tell them how long off in the future that would be. He did give them signs to look for. And they knew it would be in that generation before all of them died. They would know when it was getting close, but they would not know the exact day or hour. Nobody knew the exact day or hour. That's why they had to look for the signs and get out of Jerusalem when they saw them. But we should not read into the passage more than what is there. And we need to remember that these statements applied to the generation that would see the signs, which manifestly was the first century generation, because He says that that generation would not pass until all those things occurred. Since that generation passed, those events (including His return) must already have happened. Therefore, the passage about not knowing the day or hour no longer applies to us, because the return is a past event. We now know (historically) the day and hour of His return (70 A.D.). We no longer need signs to tell when it is getting close. It is a past event. That day and hour has already come.