Joel 3

This chapter speaks of many things that could have been fulfilled with the first coming, but certain portions must refer to the future time when God turns the nation of Israel back to Himself, as per Ezekiel 39 and Zechariah 14.

Notably, v17 says that foreigners will no longer invade her.  This will only come about after the Gog Magog war, when God pours our His Spirit and saves Israel.

Thus, the bulk of this chapter, and its specific fulfillment, are seen in the future.  The signs of v15 and the Lord’s roaring are seen to be the fire falling from heaven in Ezekiel 38-39, and not the same as the signs of Joel 2, or the second coming in Matthew 24.

The sun being darkened and the moon turning to blood is indeed a great sign, but appears to happen in a couple of instances.

Particularly, Joel 3:20 indicates that Jerusalem will be inhabited forever.  This precludes the assignment of Revelation 17’s “great city” as being Jerusalem, because Revelation 18 says it will be abandoned forever.