In Isaiah, chapter two, verse twelve, “For the day of the LORD of hosts shall be upon every one that is proud and lofty, and upon every one that is lifted up; and he shall be brought low.” According to Isaiah, a time of judgment was coming. The immediate fulfillment of his prophecy was God’s devastation of the land of Israel through the armies of the Assyrians and Babylonians as His agents of wrath, as in chapter thirty-nine, verse six. In a larger prophetic perspective, “the day of the Lord refers to the time when God will cast down all evil on the earth as in Joel two, verse thirty-one, “The sun shall be turned into darkness, and the moon into blood, before the great and the terrible day of the LORD come.”
“The day of the Lord is not a twenty-four hour day, but an extended period when the enemies of God are overthrown. This “day” begins when directs judgments of God fall upon the place He made toward the end of this age. The tribulation period is included in the day of the Lord. This wrath of God culminates with Christ’s coming to destroy all the wicked. The day of the Lord apparently begins at a time when people hope for serenity and security.
The “day” will not overtake faithful believers like a thief, for they are appointed to receive salvation, not wrath; they will be alert and self-controlled, living in faith, love, and righteousness. Believers are delivered from this “wrath to come” through the Lord Jesus Christ when He comes to catch the faithful of the churches and take them to heaven.
The day of the Lord will end after the millennial kingdom, at the creation of the new heaven and new earth.