If A=B=C then A=C
The Olivet discourse cannot be divided, as futurists do, to insert some far distant future 3rd or more Comings of Christ. Luke's account confirms the unity of the Olivet discourse. Lk 21:20-22 was the time when the Son of Man was revealed. This of course should already be abundantly clear because these were "…the Days of Vengeance that all things which are written may be fulfilled." [Lk 21:22].
[A] Lk 21:20-21 But when you see Jerusalem surrounded by armies, then know that its desolation is near. Then let those who are in Judea flee to the mountains, let those who are in the midst of her depart, and let not those who are in the country enter her. [mid 66-70AD]
[B] Mt 24:16-18 then let those who are in Judea flee to the mountains. Let him who is on the housetop not go down to take anything out of his house. And let him who is in the field not go back to get his clothes. [parallels Lk 21:20-21]
[C] Lk 17:30-31 Even so will it be in the day when the Son of Man is revealed. In that day, he who is on the housetop, and his goods are in the house, let him not come down to take them away. And likewise the one who is in the field, let him not turn back. [parallels Mt 24:16-18]
If – [A] Lk 21:20-21 = [B] Mt 24:16-18
And – [B] Mt 24:16-18 = [C] Lk 17:30-31
Then – [A] Lk 21:20-21 = [C] Lk 17:30-31
The rules of logic demand that if A=B and if B=C, then 'A' must = 'C.' This beyond doubt proves that Lk 21:20-22 was the "The Day in which the Son of Man was revealed" i.e., His 2nd Coming, precisely as Luke 17:30-31 indicates. The time when the Judean Christians fled city and countryside, departing from roofs and fields, not stopping nor turning back, was indeed the Day when the Son of Man was revealed. We have this unequivocal fact according to Lk 17:30-31, which parallels Mt 24:16-18, which again parallels Lk 21:20-21. With Scripture interpreting Scripture, we find the mid 66-70AD time frame to be the time when the 'Son of Man' was revealed in judgment against Old Covenant apostate Judaism i.e., the Law, Sin and Death.
2Tim 4:1 I charge you therefore before God and the Lord Jesus Christ, who will judge the living and the dead at His appearing and His kingdom:
Christ's appearing or manifestation – being "revealed," is an event concurrent with the "judgment" of the living and the dead i.e., "resurrection" and His "kingdom" and are all Biblically coupled to Christ's end-time Parousia.