D&C 77 is a section in which Joseph Smith asked the Lord questions about the meaning of various parts of Revelation.
As I studied this section, I happened to notice that the section summary for v12-14 says “Christ will come in the beginning of the seventh thousand years.” So I went looking at those verses to see where it says or implies that.
12 Q. What are we to understand by the sounding of the trumpets, mentioned in the 8th chapter of Revelation?
A. We are to understand that as God made the world in six days, and on the seventh day he finished his work, and sanctified it, and also formed man out of the dust of the earth, even so, in the beginning of the seventh thousand years will the Lord God sanctify the earth, and complete the salvation of man, and judge all things, and shall redeem all things, except that which he hath not put into his power, when he shall have sealed all things, unto the end of all things; and the sounding of the trumpets of the seven angels are the preparing and finishing of his work, in the beginning of the seventh thousand years—the preparing of the way before the time of his coming.
A. They are to be accomplished after the opening of the seventh seal, before the coming of Christ.
14 Q. What are we to understand by the little book which was eaten by John, as mentioned in the 10th chapter of Revelation?
A. We are to understand that it was a mission, and an ordinance, for him to gather the tribes of Israel; behold, this is Elias, who, as it is written, must come and restore all things. (D&C 78:12-14)
The thing that makes us think that the second coming happens at the beginning of the opening of the seventh seal is that bit at the beginning of the v12 answer that says “in the beginning of the seventh thousand years will the Lord God sanctify the earth, and complete the salvation of man, and judge all things, and shall redeem all things, except that which he hath not put into his power, when he shall have sealed all thing…”
We think “sanctifying the earth” must be the Millennium. We think “completing the salvation of man” must be the resurrection, and “judging all things” must be the judgment of the wicked, and “redeeming all things” must be a repeat about the resurrection, or else a reformation of all systems and institutions to follow righteous principles, and we think none of these can happen unless the Lord comes first.
The thing is, the actual interpretation of the trumpets is they are “the preparing of the way before the time of his coming.” And then the events of Revelation 9 are to be after the opening of the 7th seal and before the coming of Christ. And the eating of the book in Revelation 10 is about gathering the tribes of Israel, which would also be before the coming of Christ. All these things in later chapters are before the coming of Christ.
So the question becomes--In what way, then, does the Lord sanctify, save, judge, and redeem all things in the beginning of the 7th thousand years without actually coming? I think He will do it through His prophets and priesthood holders, who prepare the way for the time of His coming.
The thing is, that bit about the Lord sanctifying the earth, completing the salvation of man, judging all things, and redeeming all things makes it seem like Christ forces it all to happen. But really, sanctification, salvation, and redemption doesn’t happen without man doing their part of coming to Christ, repenting, and asking for His grace. We have to be obedient, and the more obedient we become, the more we are prepared, and the more the Lord can do his work in our lives.
So, long story short, the beginning-section summary for those verses is an incomplete understanding. Instead, it should probably say something like, “Prophetic messages from God prepare the earth for Christ’s second coming.”