Joel’s theme is the day of the Lord that will come upon Judah and the nations. He uses Judah’s dreadful experience of a recent locust plague to illustrate the devastation that awaits the nation if they do not humbly turn to the Lord in repentance and obedience. The day of judgment upon Judah is seen in terms of a coming locust plague, and the Lord appeals through His prophet to “return to me with all your heart, and with fasting, weeping and mourning” (2:12). Images of disaster are prominent in this book, including not only locust plagues, but also famine, fires, invading armies, and phenomena in the heavens. After their judgment is completed, the people of Judah and all who call on the name of the Lord will be saved (2:32).
Handbook to Scripture: 365 Key Chapters in the Bible
https://kenboa.org/product/handbook-to-scripture-365-key-chapters-in-the-bible/
"Teach us to number our days, that we may gain a heart of wisdom."