Whereas the disciples asked the resurrected Christ when the kingdom would be restored to Israel (now, or later), in the very next verse Jesus said they were asking about something that only the Father held in his power to decide. The Son is not the Father, nor had the Son yet returned to heaven to be beside the Father. That happened a few minutes later, after he had instructed them to remain in Jerusalem to await the power of the Holy Spirit, then they would have a job to do.
Jesus did not give a direct answer to their question, because their question was limited due to lack of understanding. Jesus knew that, and also that it would be the work of the yet-to-come Holy Spirit to enlighten them and explode the concept of the Kingdom into the magnitude needed to get their commissioned global work done.
The start of expanding their understanding began minutes later when they saw Jesus ascend bodily up into the sky, until clouds hid him from their view. Then two angelic ones gave them some vital information. Next stage was the reception of the Holy Spirit, and then clarity came.
That is why Jesus did not reprimand them for their lack of understanding. He knew understanding would begin minutes later, continuing days later with the Holy Spirit reminding them of things Jesus had said earlier, and teaching them. Jesus had said that before his death, to them directly, in John 14:16-17 & 26; 15:26-27; 16:13-14.
Now it may become clear that Jesus was not speaking about "an event" in Acts 1:7, for he knew of a series of events that must fist happen before the disciples could begin to properly understand what the Kingdom of God was really all about. Jesus spoke about timing. The disciples were not entitled to know the Father's timing, but they experienced a few minutes later the start of a series of events that would teach them, and expand their thinking. They would move on from a restricted idea about the nation of Israel having the former earthly kingdom 'restored'. Jesus was not restricted to being King of an earthly kingdom centered on the tiny little nation of Israel! Dear me, no! Christ is King over all Creation! (Revelation 3:14 & 17:14 & 19:13-16) But full understanding had to come over time, as the Holy Spirit reminded them of Jesus' teaching, and the significance of the resurrection and his ascension to heaven dawned.
By the time the apostle John wrote that Revelation, clarity had come, even though they still had not been given any exact date, time, or season. They had been informed what to expect, and the final glorious outworking of the Kingdom of God, with Christ its King.