It is 42 years in Revelation, half of seven years. Daniel 9:27 the confirming of the Mt. Sinai covenant is for 7 years, as that is cycle that Moses required it be done in Deuteronomy 31:9-13.
Also the "week" of Daniel 9:27 has to be 7 years in order to fit the 2300 days of Daniel 8:12-14 into it.
The NT is the only Covenant in Daniel 9.
Daniel 8:12-14 is not about the 7th Trumpet.
Daniel 8 was Hanukkah, the event that made it necessary for a cleansing of the Temple was Antiochus Epiphanes. Daniel 8 was the well known event that Jesus was alluding to in Matthew 24:15. Such an occurrence will happen when the Atonement Covenant is confirmed at the 7th Trumpet. Or those 42 months will not happen at all. Daniel 8 was already fulfilled. Matthew 24:15 is still future and not a set period of time, like what happened, that is commemorated by Hanukkah.
The week in Daniel 9:27 is a week of days, not years. Daniel 9 is the oasis of hope in the midst of earthly kingdoms doing violence and God's judgments. But that hope will not be full and truly describing earth until all of Adam's dead corruptible flesh is removed at the Second Coming.
While the Cross was the physical point in time for us to see God at work in redeeming mankind, the Second Coming will be the lifting of the spiritual veil that is preventing us from seeing the entire plan at work on the earth. There is no going back to confirm anything from Mount Sinai.
Paul said Sinai was:
"For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman. But he who was of the bondwoman was born after the flesh; but he of the freewoman was by promise. Which things are an allegory: for these are the two covenants; the one from the mount Sinai, which gendereth to bondage, which is Agar. For this Agar is mount Sinai in Arabia, and answereth to Jerusalem which now is, and is in bondage with her children. But Jerusalem which is above is free, which is the mother of us all."
The Law of Moses was under the bondage of sin. The NT is the Covenant that is confirmed in Daniel 9:27. Jesus confirms this Atonement agreement that was in place before creation itself. That is why the Lamb's book of life was unsealed. That is why the final harvest happens during the Trumpets and Thunders. This 7th Trumpet confirmation is to determine who is still named in the Lamb's book of life, and who will be removed. At the point of the 7th Trumpet those beheaded are still in the Lamb's book of life. But the confirmation is to see if there are any left who will be beheaded. If God in His foreknowledge confirms there are no souls left who will choose to be beheaded instead of taking the mark, then that is the end. There will be no 42 month extension of grace and mercy. So saying this 42 months or 1260 days has to happen, means you know there will be some who will be beheaded. Not because John said it would happen. You have to know the future not written. John saw the worse case scenario.
And even before the 7th Trumpet, John saw 7 Thunders, that he was not even allowed to write down in the book of Revelation.
So not even the church, nor those of Israel, will be on earth at that time, as that time does not even pertain to them. Nor were we told what to even prepare for. The best news we can give the lost is that God will kill them all and send them to the LOF. At least from the book of Revelation. The good news is in the Gospel.