The event that marks the end of the Great Tribulation is the darkening of the sun and the moon.


This agrees with the Sixth Seal of Revelation.


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 heaven shall be shaken."


The day of God's wrath begins with the darkening of the sun and the moon.


Read Revelation 6:12-17 and Acts 2:20