In Revelation 1, John was taken by the Spirit into the Lord’s Day. He began the Book of Revelation with its climax—the climax of our faith. It is this Day that every Christian looks forward to.
But why has John called it “the Lord’s Day” and not “the Day of the Lord?” The answer is revealed in the statement “I am the Alpha and the Omega,” which appears in verse 8.
God was the Lord in the Old Testament. He was called Adonai Yihvah, the expression we read in our Bibles as the Lord God, as in Isaiah 61:1—“the Spirit of the Lord God is upon Me.”
After Jesus endured the cross, God made Him the Lord, as Peter explained in Acts 2:36 and as Paul explained in Philippians 2:9. After Jesus rose, He said, “All authority has been given to Me in heaven and earth.”1Matt 28:19
On the Lord’s Day, God will become the Lord again. He is the First and the Last.
This is dramatically illustrated of Revelation, where the apostle John never calls Christ the Lord in the Lord’s Day or thereafter! In Revelation 11:8, 14:13, 17:14, and 19:16 John calls Christ the Lord, but after the Lord’s Day, in Revelation 1:8 and 10, 4:8 and 11, 11:15 and 17, 15:3 and 4, 16:7, 18:8, and 22:5 and 6, John called God “the Lord.”
In the New Testament, there are about 500 uses of the phrase “Lord,” and only Christ is called “the Lord” after His resurrection, and before the Lord’s Day, except when referencing Old Testament passages or calling God the Lord of Creation.
The apostles used the expressions “Day of the Lord” and “Day of Christ” to signify the Day of Christ’s return, but when speaking of the Father, Peter called this Day “the Day of God”22Pet 3:12 to signify the Day of destruction. It seems that John called it “the Lord’s Day” to signify the Day when God becomes the Lord again.