The rapture of the faithful (saints) is the gathering together of the dead faithful & living faithful.
1 Thessalonians 4
(13) But I would not have you to be ignorant, brethren, concerning them which are asleep, that ye sorrow not, even as others which have no hope.
(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 (the gathering / harvest) with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.
The subject of the above is the concern of whether the faithful who have died (sleep) are included in the rapture (gathering / harvest).
The faithful dead will be gathered WITH the faithful living.
1 Corinthians 15
(50) Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.
(51) Behold, I shew you a mystery; We shall not all sleep, but we shall all be changed,
(52) In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
Matthew 24
(29) Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken:
(30) And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory.
(31) And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other.
To determine when this event happens, all one has to do is determine when God will raise the faithful dead incorruptible, for that is the time the faithful living will be gathered with them.
There are already several clues in the above passages. But there are several specific passages that say when the faithful dead are raised incorruptible --- the last day.
John 6
(39) And this is the Father's will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day.
(40) And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day.
John 6
(44) No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day.
John 6
(54) Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day.
John 11
(24) Martha saith unto him, I know that he shall rise again in the resurrection at the last day.
Now, there is only one raising / gathering / harvest of the faithful --- the last day.
So, is the last day before or after the tribulation?