"It is not a new gospel that is to be proclaimed to the last generation, but the same "everlasting gospel."
In the first of these three messages, however, there is, connected with the proclamation of the gospel, a new reason assigned why men should yield obedience to the Lord.
It is found in these words: "For the hour of His judgment is come." (Rev.14:7) 
---This first angel's message does not say the judgment is coming,
---but "the hour [period] of His judgment is come."
Such an announcement could only be made at a time when the judgment is actually to begin. If men are to give such a message to their fellow men, the Scriptures must contain a line of prophetic truth, and a prophetic period leading down to the session of the judgment.
Q: Do the Scriptures contain such a period?
A: They do, or men could never, from the Scriptures, give such a message.
---That period of time is the 2,300 days, leading down to the cleansing of THE SANCTUARY....The work of mediation in the earthly sanctuary was a representation, in figure, of the real work of Christ, the true High Priest, as He pleads before His Father, in the heavenly sanctuary, for those who, with truly contrite hearts, confess their sins to Him. ...So this final work of Christ, as the true High Priest, in blotting out the sins of God's people - the cleansing of the heavenly sanctuary - must be the passing of judgment on their cases." J.N. Loughborough