Many modern teachers of eschatology (study of last things) will tell us that the “great and terrible day of the Lord” (Joel 2:31; Malachi 4:1) is yet in our future. However, if we take the New Testament writers at their word, the great and terrible day of the Lord has already past. It is not in our future. The book of Malachi has had tremendous influence over the eschatology of the New Testament writers. For example, in the day when the Messiah suddenly comes to his Temple and purifies the sons of Levi that they may offer offerings acceptable to the Lord, the question is asked: “Who will be able to stand?” (Malachi 3:1-3).
The implication is that when Messiah comes it will be for both judgment and vindication. He claims he will sit in judgment and be a swift witness against the unrighteous who oppress the widow, the fatherless and the stranger (Malachi 3:5). This charge demands national judgment according to the Law of Moses (Exodus 22:21-24; Deuteronomy 27:19), and Malachi asks: “Who may abide the day of his coming? and who shall stand when he appears?”
John tells us in the Apocalypse that there would be a great earthquake and the sun would become black and the moon turned to blood (Revelation 6:12; cf. Joel 2:31). The stars would fall from the heavens to the earth and heaven would be rolled up like a scroll (Revelation 6:13-14; Isaiah 34:4). The great and mighty would flee to the mountains seeking shelter among the rocks and caves (Revelation 6:15-16; Isaiah 2:19; Hosea 10:8), because the great day of the Lord’s wrath had come “and who shall be able to stand” (Revelation 6:17; Malachi 3:2). So, because Israel had violated the covenant they made with God (Malachi 3:5; Exodus 22:21-24), they brought upon themselves national judgment, and John sites Malachi 3:2 to say that that judgment was very near (Revelation 6:17; 22:6, 10, 12), and the judgment upon Jerusalem and the Temple in 70 AD fits the prophecies of Malachi and the other Old Testament prophets perfectly.
Malachi also predicted the coming of Elijah before the great and terrible day of the Lord (Malachi 4:5-6), but why is this important? All Biblical scholars agree that Malachi’s Elijah was John the Baptist. Jesus, himself, even told his disciples that Elijah had already come in the first century AD, and Jesus’ Apostles understood him to mean John the Baptist (Matthew 17:11-13). The point is that absolutely nowhere in scripture do we find anyone predicting the coming of two great and terrible days of the Lord. If this is true, and Elijah had already come in the time of Jesus, then the Great and Terrible Day of the Lord had to have been in the first century AD, and Jesus’ judgment upon Jerusalem and the Temple (cf. Matthew 26:64) in AD 70 fits that judgment.
Moreover, since John predicted the coming of the Kingdom of God, judgment upon Israel, and the resurrection of the dead (viz. the time of the harvest), then all these things must have been fulfilled in the first century AD (cf. Matthew 3:7-12).
Finally, notice what Malachi says about the books of judgment:
Then they that feared the LORD spoke often one to another: and the LORD hearkened, and heard it, and a book of remembrance was written before him for them that feared the LORD, and that thought upon his name. And they shall be mine, says the LORD of hosts, in that day when I make up my jewels; and I will spare them, as a man spares his own son that serves him. Then shall ye return, and discern between the righteous and the wicked, between him that serves God and him that serves him not. (Malachi 3:16-18)
This scripture has a direct relationship with Revelation 20:11-15, which many refer to as the great white throne judgment. Notice also that the books are opened at the end of what is called the millennium. Yet, Malachi says this will occur when the Lord suddenly comes to his Temple (Malachi 3:1), when he had purified the sons of Levi that they might offer acceptable sacrifices to the Lord (Malachi 3:3), and this would be when he came to judge the nation for breaking the covenant they made with him (Malachi 3:5). He did this is 70 AD in the great and terrible day of the Lord, by conquering Jerusalem and destroying the Temple, thus ending the Old Covenant and establishing the New.
 Pulpit Commentary; Poor Man’s Commentary; Matthew Henry; Ironside Notes on Selected Books; Jamison, Fausset and Brown; Albert Barnes Notes; Adam Clarke; Expository Notes of Dr. Constable, to name some.