I looked when He broke the sixth seal, and there was a great earthquake; and the sun became black as sackcloth made of hair, and the whole moon became like blood; and the stars of the sky fell to the earth, as a fig tree casts its unripe figs when shaken by a great wind. The sky was split apart like a scroll when it is rolled up, and every mountain and island were moved out of their places. Then the kings of the earth and the great men and the commanders and the rich and the strong and every slave and free man hid themselves in the caves and among the rocks of the mountains; and they said to the mountains and to the rocks, "Fall on us and hide us from the presence of Him who sits on the throne, and from the wrath of the Lamb; for the great day of their wrath has come, and who is able to stand?” (Rev. 6:12–17)
We know because we have seen the sign in the sun, moon, and stars that the Day of the Lord will soon follow, for the prophet Joel informed us that this sign would take place before the Day.
The sun will be turned into darkness and the moon into blood before the great and awesome day of the LORD comes. (Joel 2:31)
The fact that the Day of the Lord cannot take place until after the sign in the sun, moon, and stars verifies that the time period previous to this is not aimed at the enemies of God, “those who dwell on the earth.” Never is there a biblical mention of end-times wrath that will precede the Day of the Lord. When the subject is God’s wrath, it is always the Day of God that the evil men are warned about.
Since the Day of the Lord has not begun before the sixth seal, no wrath is being poured out upon the earth dwellers, and He is not judging or avenging the blood of the martyrs, so the “test” for them couldn’t possibly be under way, no matter what pre-trib teachers proclaim. But once the sixth seal is opened, the triple sign in the sky is displayed, and the sky opens up like a scroll, it is time for the earth dwellers to fear. It’s time for them to hide themselves in the caves and among the rocks of the mountains, and from the presence of Him who sits on the throne, because the time has come—it is now about them! The hour of testing has arrived to test those who dwell on the earth.
I have connected the two passages in question to simplify what I believe is being taught.
…“How long, O Lord, holy and true, will You refrain from judging and avenging our blood on those who dwell on the earth?”…And they were told that they should rest for a little while longer, until the number of their fellow servants and their brethren who were to be killed even as they had been, would be completed also...Then God will avenge their blood by throwing those who dwell upon the earth into the hour of testing, that hour which is about to come upon the whole world, to test them.
And fortunately, we will be “kept from” the hour of testing because we will be rescued from the wrath to come (1 Thess. 1:10). When we see the triple sign in the sky we will know
that our redemption draws near (Luke 21:28). The sky will split apart (NASB) and recede (NIV) like a scroll (Rev. 6:14), and relief will be given to the afflicted as Christ is revealed from heaven with His mighty angels (2 Thess. 1:7). Christ will gather us from the furthest end of the earth to the furthest end of the heaven (Mark 13:27), and His presence will make the inhabitants of the earth fear for their lives and recognize that the wrath of God has come (Rev. 6:16). The test will begin, and all who have worshiped the beast will fail the test and pay the penalty of eternal destruction, away from the presence of the Lord and from the glory of His power, when He comes to be glorified in His saints on that day (2 Thess. 1:8-9).
For added detail and possibilities, I suggest the following three articles.
Dave Bussard is the author of Who Will Be Left Behind and When?, available from Strong Tower Publishing.