D&C 77
I had always envisioned that the 7th seal would be broken at the coming of Christ. We are explicitly told that the 7th seal is broken and the 7th thousand years of temporal existence for the earth begun before the Calamities of Revelation chapter 9 which precede the coming of Christ.
Let me just say that I want the Seal of the Lord in my forehead before that happens. (Those who do will not receive the pestilence of the scorpions.)