It will start after the AntiChrist is revealed and then known to the world, and after the agreement between the Jews and Arabs is concluded ... whether by mutual agreement or by an imposed agreement (it could seen as being done either way).
Another indicator that we’re in the Tribulation is when you see “ground being broken” for the construction of the Third Temple.
Another indicator of being “in the Tribulation” is when you see those “two witnesses” in Jerusalem, giving God’s message to the world and that no one can arrest them or hamper them from doing that.
Another indicator of “being in the Tribulation” is when you see 12,000 Jews each group being from the 12 Tribes of Israel (being a total of 144,000 Jews), going out to the world, giving the Message of the Gospel of the Salvation of Jesus, the Messiah of Israel.
If someone can run down that list and show me where that’s the case with each one of them ... THEN I’ll know I’m in the Tribulation.
That’s the point: Christians are raptured BEFORE the tribulation. When these things happen, we’re already gone.