An expression used by Old Testament prophets to describe a time when God will intervene in history, mainly for judgment. Thus, “the day of the Lord” is also called “the Day of the LORD’s anger” (Zephaniah 2:2). This expression appears in the writings of the prophet Amos, who lived during the eighth century BC.
The Day of the Lord in the Old Testament
Sometimes, “the day of the Lord” is used in the Old Testament to refer to a previous judgment (Lamentations 2:22). However, it usually refers to a future judgment (Joel 2:1–11). Specifically, it refers to the final judgment of the world (Joel 3:14–21; Malachi 4:5). Often, a prophecy about an event in the near future is combined with an end-time prophecy—a coming judgment is a preview of the final Day of the Lord. Isaiah's prophecy against Babylon in Isaiah 13 is an example (Isaiah 13:5–10). Jesus used many prophecies to explain his second coming (Mark 13:24–37).
Another example is Joel’s prophecy of the Day of the Lord (Joel 1:15–2:11). The prophet predicted a plague of locusts God would send to Israel, but his prophecy extended to the Day of the Lord after Joel’s time (Joel 2:14–17, 31). The Day of the Lord was even after the outpouring of the Holy Spirit at Pentecost, which was also predicted by Joel’s prophecy (Joel 2:28–32; Acts 2:16–21; Revelation 6:12–13). The New Testament only uses the term to mean the end times.
The Day of the Lord is described as a day of gloom, darkness, and judgment. It is connected to God’s judgment and describes changes in nature, such as the darkening of the sun, moon, and stars (Isaiah 13:10; Joel 2:31; 3:15; Matthew 24:29; Revelation 6:12). Nations will be judged for their rebellion against Israel (Joel 3:19; compare Psalm 2). However, Israel is told not to be eager for that day because they will also be judged (Amos 5:18–20). But the prophets promise that a faithful “remnant” will be saved when they turn to the Messiah (Joel 2:32; Zechariah 12:10). After the judgment is a time of prosperity, restoration, and blessing for Israel (Joel 3:18–21).
The Day of the Lord in the New Testament
There are more explicit expressions in the New Testament:
“The day of our Lord Jesus Christ” (1 Corinthians 1:8)
“The day of the Lord Jesus” (1 Corinthians 5:5; 2 Corinthians 1:14)
“The day of Christ” (Philemon 1:10; 2:16)
These are more personal and positive. They refer to final events for Christian believers, who will not experience God's wrath (1 Thessalonians 5:9). When the Day of the Lord comes, the earth will be renewed and purified with fire (2 Peter 3:10–13). In Revelation, this final purification comes after the Millennium—that is, the 1,000-year reign of Christ (Revelation 21:1).