“The day of the Lord will come as a thief in the night.” The day of the Lord is mentioned a couple dozen times in the Bible and is a significant idea in the study of end times. The term may be a little confusing because it is not actually referring to a single day, but a period of time. This phrase is an idiom, a phrase that means something other than the literal meaning of its words. Calling someone your sweetheart is an idiom. The literal meaning of a sweetheart- a sugary, blood pumping organ has nothing to do with the idiomatic meaning of sweetheart- someone you love deeply. Likewise, the day of the Lord is not an entirely literal phrase. It is an idiom referring to a period of Divine judgment.
The phrase is used in the Old Testament to refer to several different kinds of judgment. It is used to describe the judgment of Israel (Amos 5:18-20) and Judah (Ezekiel 13:6) for their idolatry. In the book of Obadiah the day of the Lord is used to describe God’s judgment upon certain Gentile nations. (Obadiah 1:15)
In most cases the day of the Lord is used to describe the return of Jesus to earth in judgment and to establish His millennial kingdom. The Bible describes several specific events as making up the day of the Lord. The seven years of the Tribulation (Joel 2:31; Matthew 24:21, 29; Revelation 6:12-13), the second coming of Jesus to the earth (Zechariah 14:1-2; Revelation 19:11-15), the thousand year reign of Jesus over the earth (Zechariah 14:8-11; Isaiah 11) and the destruction of this universe (2 Peter 3:10).
The most lengthy single description of the day of the Lord is found in the book of Revelation. Almost all of the events foretold in chapters 6 to 20 of Revelation take place during the day of the Lord. The day of the Lord is described as a day of judgment (Matthew 25:31-46), of vengeance (Isaiah 34:8), of fierce anger (Isaiah 13:9) and of darkness (Acts 2:20). The day of the Lord will include the battle of Armageddon, a great battle against Jerusalem (Zechariah 14:2; Joel 3:14). The day of the Lord is a great and terrible day (Joel 2:11)
The day of the Lord will also be a day of restoration, of peace and of righteousness. (Zechariah 14:16-21). During that day the world will be restored to a portion of the perfection it had before man sinned, including the absence of predators and venomous creatures (Isaiah 11:6-9), long life (Isaiah 65:20) and the removal of all sorrow (Isaiah 65:19). In the day of the Lord Israel will no longer worship false gods. Jerusalem will be the center of universal worship of Jesus as God and King.
The day of the Lord will come suddenly and unexpectedly. The coming of the day of the Lord is repeatedly described as coming without warning, like a thief in the night (Luke 12:39-40; 1 Thessalonians 5:2; 2 Peter 3:10) When the world is going about life as usual, with little thought to the things of God, then Jesus will return. The suddenness of the day of the Lord teaches us to ready ourselves now for that terrible day. We must heed the warning given by Peter in Acts 2:20-21. We must turn to Jesus and call upon Him for salvation from His wrath.