The expression "Lord's Day" appears only once in the Bible, in Revelation 1:10:
I was in the Spirit on the Lord’s Day, and I heard behind me a loud voice, as of a trumpet,
“Write the things which you have seen, and the things which are, and the things which will take place after this.
There are various interpretations about what this expression means, the most common being that it refers to a specific day of the week.
- Sunday: Every reference to Sunday in the Greek scriptures is "the first day of the week" (meaning from sunset on Saturday to sunset on Sunday).
- Saturday: Hebrews 4:4 uses the expression "seventh day", and all other references are "sabbath".
- Why would John introduce new terminology, completely out of context, to indicate the day of the week?
- Why would John even bother to mention what day of the week it was?
Only someone that had grown up in a church that refers to Sunday as the "Lord's Day" would let this experience influence their interpretation of what John wrote.
That method of reasoning is known as confirmational bias, and with respect to scriptural analysis as eisegesis.
When trying to prove or derive the meaning of something, such reasoning is very unreliable.
On the other hand, a far more reliable method is abductive reasoning (looking at things in context, including people's motives) and exegesis.
In this case, a reasonable man would answer the above questions with "he wouldn't".
And the obvious objective conclusion is that John wasn't using "Lord's Day" to refer to a specific day of the week.
Another way of expressing "Lord's Day" is "Day of the Lord", and that expression does appear many times in scripture.
Isaiah 58:13 uses the expression to refer to the Sabbath day:
… My holy day, and call the Sabbath a delight, the holy day of the LORD honorable …
but that appears in only some translations, and it is only one occurrence.
All 24 other uses of the expression have a completely different meaning, such as:
- Behold, the day of the LORD comes, Cruel, with both wrath and fierce anger, To lay the land desolate; And He will destroy its sinners from it. — Isaiah 13:9
- For this is the day of the Lord GOD of hosts, A day of vengeance, That He may avenge Himself on His adversaries. The sword shall devour; It shall be satiated and made drunk with their blood … — Jeremiah 46:10
- … For the day of the LORD is at hand; It shall come as destruction from the Almighty. — Joel 1:15
- The sun shall be turned into darkness, And the moon into blood, Before the coming of the great and awesome day of the LORD. — Joel 2:31
- For the day of the LORD upon all the nations is near … — Obadiah 1:15
- The sun shall be turned into darkness, And the moon into blood, Before the coming of the great and awesome day of the LORD. — Acts 2:20
- For you yourselves know perfectly that the day of the Lord so comes as a thief in the night. — 1 Thessalonians 5:2
- But the day of the Lord will come as a thief in the night, in which the heavens will pass away with a great noise, and the elements will melt with fervent heat; both the earth and the works that are in it will be burned up. — 2 Peter 3:10
These, and many other scriptures are talking about the end time, when Jesus returns to destroy the wicked and save the righteous.
This time, the Day of the Lord, is exactly what John's vision was all about.
John even makes frequent use of the same imagery to describe it:
- … For in one hour she is made desolate. — Revelation 18:19
- … drunk with the blood … — Revelation 17:6
- … And should destroy those who destroy the earth. — Revelation 11:18
- … the sun became black as sackcloth of hair, and the moon became like blood — Revelation 6:12
- … to him I will give power over the nations — Revelation 2:26
- … I will come upon you as a thief, and you will not know what hour I will come upon you.— Revelation 3:3
- … And fire came down from God out of heaven and devoured them. — Revelation 20:9
- … Then Death and Hades were cast into the lake of fire. This is the second death. And anyone not found written in the Book of Life was cast into the lake of fire. — Revelation 20:14–15
- Now I saw a new heaven and a new earth, for the first heaven and the first earth had passed away. … — Revelation 21:1
Now consider these passages:
- in a moment, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, and the dead will be raised incorruptible, and we shall be changed. — 1 Corinthians 15:52
- For the Lord Himself will descend from heaven with a shout, with the voice of an archangel, and with the trumpet of God. … — 1 Thessalonians 4:16
- I was in the Spirit on the Lord's Day, and I heard behind me a loud voice, as of a trumpet, — Revelation 1:10
It would be very difficult to argue that they, and all of Revelation, are not describing the same event, the Day of the Lord, a period of time that begins with Jesus's return and ends with the destruction of this world.