It is not for you to know the time.
Acts chapter 1 is often used as a reason why we cannot know the dates surrounding the return of Jesus. Jesus told the disciples it was not for them to know the times. This charge does not exclude a later generation from knowing. Jesus also included one of the signs that would identify his soon return.
Background
Acts chapter 1 is often quoted by folks trying to dismiss out of hand the study of time in the Bible. In this passage Jesus is asked a question. Is he, at that time, going to restore the kingdom to Israel?
This question was important to ask, since this is what the angels had told Mary before he was born. This is also what John the Baptist had preached about Jesus. Now they ask the question, "When are you going to do what all these others have said you are going to do?"
Jesus’ Answer
The answer Jesus gives is long, with several components. Lets look at it in detail. He says first, that they will receive the Holy Spirit. This is the first part of his answer to the question. He is saying that the Holy Spirit is where the final answer will come from. Then he says that the Gospel will be preached, in Jerusalem, in Judea and Samaria, and to the ends of the earth. This answer is in fact the answer to when will he take over the kingdom. After, and only after, Christians have witnessed of him and his resurrection in every nation on earth. Then he will restore the kingdom to Israel. Like the fig tree in Matthew and Luke, the world wide proclamation of the Gospel is the sign used by the writer of Acts to signal Jesus’ soon return.
Why would the writer of Acts choose this sign? Because the book of Acts documents the beginning of this process, the movement of the Gospel from Jerusalem to Judea and then to Samaria and from there to the ends of the earth. Curiously the Gospel, Christianity, did not move much beyond the borders of Europe until the last 300 years or so. Only now are we seeing national conversions on a scale not seen since Europeans adopted Christianity 1700 years ago. Why? Because it is only now that the Gospel is headed for the ends of the earth. This is the sign that the author of Acts wants us to use, not the fig tree of Matthew and Luke. (OK, Luke and Acts have the same author, his focus has now changed.)
Until very recently Acts chapter 1 was a legitimate reason why we today, could not know when Jesus was returning. Now, in the mid 1990s, Acts chapter 1 is prophecy about Jesus’ soon return. The reason? Because the Gospel is now being preached in the uttermost parts of the world. Is this the same as 1700 years ago in Europe? No, because now there are no parts of the world that are farther away. We really are at the last most distant corners of the world.
Interestingly, until about 1990, nobody even knew who the uttermost parts of the world were. Now we have missionary movements attempting to share the Gospel with every people group over about 10,000 people. By the end of the first decade of the 21st century most people on the planet will have met know or know of a Christian somewhere in their lives. The events of late 2002 will put witnesses of Jesus’ power and greatness in every hamlet round the globe. Then the world will have achieved this event described in Acts. The sign given in Acts will then be complete, and for the general purposes of that sign he can return.
It is interesting to note that until the decade of the 1990s we did not even know who these people groups were. What a difference just a few years can make.
Does Acts chapter 1 tell us when Jesus is coming back? No, but it certainly does not tell us that it cannot be known. Only that those alive in the first century could not know it. The signs Jesus then proceeds to give point at our century, in fact they point at the first decade of the twenty first century as the main sign of his return.