The Lord's Day = The Day of the LORD

I INEVITABLY came to this conclusion, finally.

With emphasis but never the essence placed differently, The Lord's Day equals The Day of the LORD, which equals The Last Day, in all the Scriptures.

If ever there was an 'application' of some 'Sabbath-principle' in the Scriptures, it applies to this equation because it is SEEN implicated and explicated in every instance of relevant Scriptures ---which without exception culminates in the imperative final extent of the equation:
The Lord's Day = The Day of the LORD = The Last Day = The Seventh Day = "The Sabbath-Rest-Day OF THE LORD GOD" = JUDGMENT DAY.

Isaiah 66:23,24 indisputably, incontrovertibly and irretrievably proves the point ... and proves it with everlasting implications and applications for him who reads. Take it or leave it, the truth of it is going to have everything its own way!

Ja; it's a warning. The Last Day is RESURRECTION Day and Day of Reckoning; it is going to be The Sabbath DAY for both The People of God and the "transgressors" despite they're not going to like it. Because it shall be the DAY, ON which, Christ shall RETURN.