The sun darkened and the stars not giving light take place "after the tribulation" (Mark 13.24). This agrees with Rev. 11.19 at the end of the Tribulation, for the cause of the darkened sun and stars is due to great stormy weather: "lightnings, rumblings, thunders, and earthquake (which has the ability to darken the sky), and sever hail (major cloud covering due to winter weather)." These natural events are pronounced. God uses nature to judge.

Revelation chapters 7 to 11 are the major elements of the 7 year Tribulation so naturally Rev. 11.19 is at the very end when Jesus steps down on the mount of olives. Revelation chapters 12 to 19 are simply the details of those major events that occur during the Tribulation. Revelation chapter 20 is what follows the Millennial Reign of Christ on earth in Person.

This is similar to how in Genesis chapter 2 & 3 gives the details of chapter 1. Chapter 1 is eternity past to creation to restoration and man; whereas Revelation 21 is eternity future.