Mat 24:35 Heaven and earth will pass away, but my words will never pass away.
Mat 24:36 "No one knows, however, when that day and hour will come---neither the angels in heaven nor the Son; the Father alone knows.
Mat 24:37 The coming of the Son of Man will be like what happened in the time of Noah.
I think it is speaking of the final great day when Christ returns,
gathering of believers and unbelievers, and the burning up of the old heaven's and earth.
2Pe 3:12 looking for and rushing the coming of the Day of God, on account of which the heavens, being on fire, will melt away, and the elements will melt, burning with heat?
Otherwise known as the Day of judgement:
2Pe 3:7 But the present heavens and the earth being kept in store by the same Word, are being kept for fire until the day of judgment and destruction of ungodly men.
For God's people it will be the return of their King.
For God's enemies, it will be their destruction.
This must be post-tribulation. Now, whether or not the church is on earth when this happens (post trib)or whether or not the church has been raptured (pre-trib)... I believe the church is on earth when this happens. I believe in post-trib rapture.
This is because Jesus's words about knowing the times, and being ready, are spoken to His followers... "you also be ready"..
If the church was already raptured, there would be no need for it to be ready.
Mat 24:44 Therefore you also be ready, for in that hour you think not, the Son of Man comes.