I’ve always understood 1’st Thessaloniki 5:3 as a reference in time during the 7 year tribulation period. A time at the beginning following the signing of a false 7 year peace covenant.
The term “they” I believe is in reference to the Jewish. This correlates with the warnings in Matthew 24 warning the Jewish of birth pangs. The woman in labor (Israel) in labor pains of deliverance as a nation. With her child (the 144,000 -12 tribes of 12,000 each. The children of Jacob and the time of Jacob’s woes.
I just don’t see how it could be speaking of the tribulation. That’s not Paul’s mission for Christ. His mission is the creation, care of it, and when and how the Body of Christ will be taken from this earth.(Rapture).
I think there is a day if the Lord for the Church the Body of Christ, when He comes aaand removes us from the wrath to come
There is a day of the Lord for those going through the tribulation and His second coming.