The Message of Joel
No one really knows when the book was written or when Joel lived The book contains two equal parts (Joel 1:2-2:17) and (Joel 2:18-27).
 The first section describes a drought and a plague of locusts which had devastated the land in Joel's time. Joel calls for sorrow and repentance which will bring help and save the people. He could not remember a time when anything like this had occurred and felt that it would probably not occur again in his lifetime. Everything had been stripped bare. No grain for food and no grapes for wine and a shortage of water. Repentance eventually brought an end to the calamities.
 Joel sees all this as a foreshadowing of the eschatalogical Day of the Lord (Joel 2:1-11. Cf.  Obad 1:15; Zeph 1:14-15; Malachi 3:2-4;  Rev 6:17). The locusts represent God's unrelenting judgement  at the close of this age. An enormous army is marching against Jerusalem (Joel 3:9-14. Cf. Isaiah 34:2, 66:18; Zech 12:8-9, 14:2; Jer 30:7; Dan 12:1; Rev 9:7-9) and this is accompanied by natural and supernatural signs such as earthquakes and atmospheric phenomena (Cf. Joel 3:15. Cf.  Amos 5:18; Zeph 1:15; Matt 24:29;  Mark 13:24, 25; Luke 21:11, 25, 26; Rev 6:12-13, 8:12). During this time the nation Israel will repent (Joel 2:15-17) and be spiritually renewed and saved (Joel 2:12-13. Cf. Zech 12:10-14, 13:1). The nations who have oppressed Israel and the Jews will be judged and punished and Yahweh himself will dwell in Jerusalem which will be central to the world (Joel 3:16-17. Cf. Zech 1:14; 8:2). He will bless the land of Israel after a long time of ruin (Joel 2:3, 18-19; 21-27; 3:18; 3:20-21. Cf. Is 51:3; Ezek 36:35;  Zech 7:14, 8:7-8, 22-23, 10:8-12). This must refer to the end of this age because God promises to end Israel's disgrace, shame and blame among the nations and never to do it again. It is only now that the Lord is beginning to bring this about after millennia of exile and oppression (Cf. Isaiah 11:11-16, 66:10-14, 20-23; Jer 16:15, 30:3; Ezek 38:14; Zechariah 8:3). The army will be destroyed by God (Joel 2:20). God will pour out his spirit upon all Israel. This was begun at Shavuot two thousand years ago but will come to complete fulfillment for Israel at the end of this age (Joel 2:28-29. Cf. Acts 2:17–21). As the NET Bible points out: "The equative language that Peter employs (“this is that”) stresses an incipient fulfillment of the Joel passage without precluding or minimizing a yet future and more exhaustive fulfillment in events associated with the return of Christ."  Accompanying this spiritual renewal will be signs and judgements upon the Earth (Joel 2:30-31), spurring repentance and prayer in the remnant (Joel 2:32).
 This prophecy is clearly pointing to the end of the age (Joel 3:1). The diaspora Jews will be returned to Israel in 'those days' and at 'that time'. Over the last century or so this has been happening at a faster and faster rate. When this reaches its climax the Lord says that he will judge the nations of the Earth on behalf of whom? Israel (Joel 3:2). For too long the nations had been interfering with and controlling the land and exiled people (Joel 3:3). Now God would judge and that included a group called 'all the regions of Philistia'. It is interesting to note that Philistines are mentioned as being around in the last days. As a punishment for the Bar Kochba revolt in the early second century AD the Roman Emperor Hadrian completely destroyed and renamed  Jerusalem as Aelia Capitolina and as an insult to the Jews he called the land Philistia which in Latin is Palestinia - Palestine. Those calling themselves Palestinians are in a sense Philistines. Interesting in the light of Joel's prophecy. Those peoples who took advantage of the Jewish exile will receive their reward (Joel 3:4-8). The Egyptians and Arabs will be ruined (Joel 3:19). What is the reason for God's judgement? It is because they scattered, enslaved and persecuted the Jews and now want to destroy Israel. But also, because they divide up God's land (Joel 3:2-3). A two state solution is an invitation to divine wrath! Israel is God's inheritance and the land his possession. Jerusalem will be the main issue leading up to the end (Zech 12:2-3) and in the end only one will rule over it when he comes and his feet will stand upon the Mount of Olives (Zech 14:4) accompanied by the angels and the redeemed (Zech 14:5, 9, 16-17. Cf.  Matt 16:27; 25:31) and Israel will finally worship and serve the Crucified One who is both Lord and God (Zechariah 12:10).