You're right; the Bible does warn us against speculating about the timing of Jesus' return, when He will establish His Kingdom of perfect righteousness and peace. Jesus told His disciples, "No one knows about that day or hour, not even the angels in heaven, nor the Son, but only the Father. ... You do not know when that time will come" (Mark 13:32-33).
We are probably just as curious as Jesus' disciples were to know when He will return. Over the centuries, in fact, many have claimed to know exactly when Jesus would return -- only to have their predictions fail. No doubt they were sincere but they had overlooked Jesus' own statement that even He didn't know when He would return.
At the same time, the Bible does tell us that certain events must happen before His return -- many of which seem to be taking place today. For example, Jesus said that "This gospel of the kingdom will be preached in the whole world ... and then the end will come" (Matthew 24:14).
Why hasn't God revealed it to us? Suppose you knew for certain that Christ's coming was still several centuries away. What difference would His return make to you then? Probably very little. But because it could happen at any moment, we should have a sense of urgency to do God's will. Jesus said, "As long as it is day, we must do the work of him who sent me" (John 9:4). Make every day count for Him.