The term "Judgment" includes a hearing or trial and the final conclusion or result of that trial. Not all are judged at once. To illustrate, the Church is now on trial or judgment. The Christian trial or judgment has been in progress since Pentecost. The faithful in this judgment shall be rewarded, as we read, "Be thou faithful unto death and I will give thee a crown of life." (Revelation 2:10.) 

The Judgment Day as applied to the world, in general, is entirely a different matter. It's obvious that the whole world could not be tried and judged within 24 hours. The Apostle says, "God hath appointed a day in which He will judge the world in righteousness" (Acts 17:31). Again we read: "That one day is with the Lord as a thousand years" (2 Peter 3:8). The judgment of the world by Christ will cover a period of one thousand years (Revelation 20:4-6). 

That the judgment of the world had not come in the Apostle Paul's day is clearly shown by his words in the Scripture above noted (Acts 17:31). This scripture clearly shows that Christ is to be the Judge of the world when he sets up his kingdom at his second coming. In Matthew 25:31-46, our Lord gave a description of the judgment of the world. He clearly taught that it would take place at His second appearing. This is conclusive proof that the world's judgment is not yet in progress.

For a more detailed study on the Judgment Day, please use the following link:  "The Day of Judgment"