The apostle John was a prisoner for the Lord on the island of Patmos, Revelation 1:9. On the island the Lord Jesus Christ showed him visions of what was to take place in John’s future (see Revelation 1:1), that is, in the course of the new dispensation. That is potentially our present, though since the present passage is about the final judgment, this vision too is still future for us.
11 Then I saw a great white throne and him who was seated on it. From his presence earth and sky fled away, and no place was found for them.