Jesus was on earth and in heaven at the same time (John 3:13) and John the apostle saw things happening thousands of years in the future. God is the beginning and the end. I don't know what others believe about God but I believe He is the end.
Are you aware that many prophecies failed in the Bible, and they were given to men directly by God?
The vision John saw was a prophecy of things to come. Yet it may or may not yet happen if the circumstances change, or what happens may be different than what John saw.
In no way does God giving man a prophecy imply that He is outside of time.