Joel 1:1 The word of the Lord that came to Joel, the son of Pethuel: Hear this, you elders; give ear, all inhabitants of the land!
We know very little about the prophet Joel. All we are told concerning him is in Joel 1:1, “The word of the LORD that came to Joel the son of Pethuel.” Joel means “Jehovah is God,” and it was a very common name. There have been some people who have jumped to the conclusion that the prophet Joel was a son of Samuel because 1 Samuel 8:1–2 says, “And it came to pass, when Samuel was old, that he made his sons judges over Israel. Now the name of his firstborn was Joel …” But if we read further the next verse tells us, “And his sons walked not in his ways, but turned aside after lucre, and took bribes, and perverted judgment” (1 Sam. 8:3). Samuel’s son could not have been the same as the prophet Joel.
Joel’s theme is “the day of the LORD.” He makes specific reference to it five times: Joel 1:15; 2:1–2; 2:10–11; 2:30–31; and 3:14–16. Isaiah, Jeremiah, Ezekiel, and Daniel all refer to the Day of the Lord. Sometimes they call it “that day.” Zechariah particularly emphasizes “that day.” What is “that day”? It is the Day of the Lord, or the Day of Jehovah. Joel is the one who introduces the Day of the Lord in prophecy. Yonder from the mountaintop of the beginning of written prophecy, this man looked down through the centuries, seeing further than any other prophet saw—he saw the Day of the Lord.
The Day of the Lord is a technical expression in Scripture which is fraught with meaning. It includes the millennial kingdom which will come at the second coming of Christ, but Joel is going to make it very clear to us that it begins with the Great Tribulation period, the time of great trouble. If you want to set a boundary or parenthesis at the end of the Day of the Lord, it would be the end of the Millennium when the Lord Jesus puts down all unrighteousness and establishes His eternal Kingdom here upon the earth.
The Day of the Lord is also an expression that is peculiar to the prophets of the Old Testament. It does not include the period when the church is in the world, because none of the prophets spoke about a group of people who would be called out from among the Gentiles, the nation Israel, and all the tribes of the earth, to be brought into one great body called the church which would be raptured out of this world. The prophets neither spoke nor wrote about the church.
J Vernon MeGee: Study notes