The body of Christ will be in the Great Tribulation. It was shortened so some of them will survive.
That is not how a thief in the night works.
The thief does not tell you the moment he arrives, and then leaves sooner cutting his time short before the police get there.
The thief in the night Second Coming gets shorter and shorter giving less time for Christ to operate after the Second Coming. Thus more are brought into the church, than if Christ had come 2 years earlier. Those saved were saved prior to the Second Coming. The opportunity for salvation last longer, and the GT gets shorter.
The Second Coming begins the final harvest. The Second Coming does not end the final harvest.
The 7th Trumpet is the firm date, that ends the final harvest. All humanity will be dead when the 7th Trumpet stops. The 7th Trumpet is not the GT. It is a literal week of days though. It is not the thief in the night moment. It is Christ celebrating the defeat of Adam's sinful flesh, that Adam passed on through Seth to all humanity. The promises made in Daniel 9:24.
"But in the days (the "week of" not years, but days, Daniel 9:27) of the voice of the seventh angel, when he shall begin to sound, the mystery of God should be finished, as he hath declared to his servants the prophets."
The 7th Trumpet does not last for 7 years, but a week of days. If this week of days is split in half, we get 42 months extended time, before the Millennium can start. So the 7th Trumpet sounds allowing for a hard time with or without the 42 months. It is a firm unchanging date. The Second Coming is what is not a firm or set date, because it is longer or shorter, allowing for the event to be unexpected like a thief in the night. Christ is not a literal thief. Christ is just coming to carry out the end of Adam's flesh and blood. An event planned by God as part of current creation. God did not declare or plan 6000 years of punishment. It was not even until Moses and Exodus that God declared Adam's punishment as 6 days like the 6 days of creation. Adam could have disobeyed at any point in those thousands of years, no?
That is what is strange about past history. There is no do-over. We will never know any different history. There will also be only one future history. Either the worst case scenario or the best case scenario. But until it happens we cannot know which one it will be.