The day of the Lord points to the thousand year reign of Christ, His second coming. The two witnesses are bringing about the restoring the nation of Israel.
Did you see this? When the summer fruit is gathered, Israel is done forever. God will not pass by them ever again.
As Jesus said, when summer is nigh, all these things (Matthew 24) are nigh at the door. And they were nigh at the door, the kingdom was taken from the Jews and Jerusalem was utterly destroyed in AD 70.
And for those who don't believe that it's already happened, how does "the end of my people of Israel" play out with the theology that God is going to reconcile Israel during the tribulation and usher them into the millennium when Amos 8 clearly says that during that time of summer, God is done with Israel forever.