The Day of the Lord includes a series of cataclysmic events leading up to the return of Jesus Christ and His forceful suppression of humanity's rebellion against God.
Prophecies concerning the Day of the Lord can at times have a former and later fulfillment. What that means is that the messages of the ancient prophets applied in part to the people to whom they were preaching, but many of these prophecies also refer to a future time when God will intervene in the affairs of mankind—a time that is yet to occur.
Many references to the Day of the Lord in the biblical books of Isaiah and Joel refer to punishment God poured out on ancient Israel and Judah. But when reading these prophecies, and comparing them with historical information, it is clear that they are dual in nature and were only partially fulfilled. These verses primarily look to the future when God will pour out His judgment on an unrepentant humanity before the second coming of the Messiah, Jesus Christ.
In end time prophecy, the Day of the Lord comes after heavenly signs (Joel:2:31), which come after the Great Tribulation (Matthew:24:29).
The prophet Zechariah was inspired to write: "Behold, the day of the Lord is coming, and your spoil will be divided in your midst. For I will gather all the nations to battle against Jerusalem; the city shall be taken, the houses rifled, and the women ravished. Half of the city shall go into captivity, but the remnant of the people shall not be cut off from the city.
"Then the Lord will go forth and fight against those nations, as He fights in the day of battle. And in that day His feet will stand on the Mount of Olives, which faces Jerusalem on the east. And the Mount of Olives shall be split in two" (Zechariah:14:1-4).
God is a God of love and mercy. But He is also a just and righteous God who doesn't compromise with evil. Instead of repenting and acknowledging their Creator, most of humanity has been snubbing their collective noses at Him in a pretense of religion and suffering the consequences. But a time is coming when He will intervene by sending Jesus Christ to rule over the nations and save us from ourselves.
Many Old and New Testament prophecies describe the coming Day of the Lord, including those of the seven trumpets in Revelation 8-11. They create a composite picture of terrible plagues, catastrophic war and a time when all nations will be brought together to be judged by God.