Please study and compare all three, and you will discover that "C" is the conclusion of "A+B", revealing that both events A+B are indeed SIMULTANEOUS.
A. 1 Thes. 4:14-17 plus
B. 1 Thes. 5:2-3 is the simultaneous event of- -
C. 2Thes. 1:7-10.
(In brief- A+B=C).
In line item "C", please notice the word when written two times.
A. 1 Thes. 4:14 For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him.
15 For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep.
16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
17 Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.
B. 1 Thes. 5:2 For yourselves know perfectly that the day of the Lord so cometh as a thief in the night.
3 For when they shall say, Peace and safety; then sudden destruction cometh upon them, as travail upon a woman with child; and they shall not escape.
C. 2 Thes. 1:7-10
7 And to you who are troubled rest with us, WHEN the Lord Jesus shall be revealed from heaven with his mighty angels,
8 In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ:
9 Who shall be punished with everlasting destruction from the presence of the Lord, and from the glory of his power;
10 WHEN he shall come to be glorified in his saints, and to be admired in all them that believe (because our testimony among you was believed) in that day.
(C= A+B)