The phrase, "The Day of the Lord," appears in eight prophetic books of the Old Testament: Isaiah, Jeremiah, Lamentations, Ezekiel, Joel, Amos, Obadiah, and Zechariah. In the New Testament, It is found in four epistles: 1 Corinthians, 2 Corinthians, 1 Thessalonians, and 2 Peter. With that number of writers using the phrase, you would think that its meaning would be clear. And even though it is found in twenty-six verses, its meaning is not.
Israel understood "The Day of the Lord" to mean the moment in time when the Messiah would appear, destroy their enemies, and establish His kingdom. To them, He would come to judge the heathen (Ezek. 30:3; Obad. 1:15). Israel saw it as the time He and His army would purge the land of the Gentiles (Isa. 13:9; Ezek 13:5; Joel 2:1, 11; Zeph. 1:18). His coming was described as a day of destruction (Isa. 13:6); cruel both with wrath and fierce anger (Isa. 13:9); a day of vengeance (Isa. 34:8); a day of terrors (Lam. 2:22); a battle (Ezek. 13:5); great and very terrible (Joel 2:11); a day of darkness (Amos 5:20); and a day when mighty men shall cry bitterly (Zeph. 1:14). Little did they know that many of these same words would be used to describe God's judgment upon them for rejecting His Messiah. The still future seven year "treaty" with the antichrist, called the Tribulation (Matt. 24:21), the Time of Jacob's Trouble (Jer. 30:7), and Daniel's Seventieth Week (Dan. 9:24-27), appears to be a part of "The Day of the Lord."
Because we have the New Testament, Christians have a different understanding of "The Day of the Lord." The Apostle Paul, in "sentencing a young man to death" (1 Cor. 5:1-5), saw that day as being a day of salvation from God's wrath. He saw it as the time when believers will rejoice with their brethren (2 Cor. 1:14). In his first epistle to the Thessalonians, he describes that day as coming suddenly, without warning, on those who are not "of the Light" (1 Thes. 5:1-11). Peter also speaks of that day coming as a "thief in the night," but he adds that "the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up" (2 Pet. 3:10).
Judging by these varied passages, I would have to say that "The Day of the Lord" involves the Rapture of the Church (1 Thes. 4:13-18), the Tribulation period of Israel's judgment (Matt. 24:3-28; Rev.Ch. 6 - 18), the Second Coming of Christ (Matt. 24:29-51; Rev. Ch. 19), the Millennial Kingdom (Matt. Ch. 25; Rev. 20:1-7, the Great White Throne Judgment (Rev. 20:11-15), and the bringing into being the "new heaven and the new earth (Rev. Ch. 21 - 22).
Today, there are three kinds of people: Jews, born-again Christians, and everyone else. "The Day of the Lord" can only be said to be "good news" to the real Christian. Unfortunately, to the Jew, and the others, some or all of it will definitely be "bad news." It is amazing that simply by believing in, and surrendering to Christ, determines whether one should worry about that day, or long for it to come. Come quickly, Lord Jesus!