The phrase, day of the Lord, is used 25 times in 23 verses in the Bible (I do not count two references to the "day of the Lord Jesus"). In scripture, it is most closely associated with the wrath of God. That is, the day of the Lord is the time when God brings long-deserved judgment on the earth. Consider these verses:
- Isaiah 13:6 Howl ye; for the day of the LORD is at hand; it shall come as a destruction from the Almighty.
- Jeremiah 46:10 For this is the day of the Lord GOD of hosts, a day of vengeance, that he may avenge him of his adversaries: and the sword shall devour, and it shall be satiate and made drunk with their blood: for the Lord GOD of hosts hath a sacrifice in the north country by the river Euphrates.
Joel 1:15 Alas for the day! for the day of the LORD is at hand, and as a destruction from the Almighty shall it come.
- Amos 5:18 Woe unto you that desire the day of the LORD! to what end is it for you? the day of the LORD is darkness, and not light.
Therefore, primarily, the day of the Lord refers to the character of the times. The day of the Lord is the time when God moves on the scene in a powerful way to execute His wrath on the earth because of the iniquities of man. As such, the day of the Lord is not meant to be a synonym for any term specifically related to a time period like the tribulation or the kingdom. It is closest in meaning to the tribulation and the time of the tribulation is certainly the day of the Lord. However, it does not need to be restricted to the time of the tribulation. The day of the Lord deals with the way in which God is deals with world at certain times. It is more than just a specific time period.
As such, the day of the Lord can refer to times of judgment that are already history. The day of the Lord in Jeremiah 46:10 has fulfillment in the defeat of the Egyptians by the Babylonians. In direct context, Jeremiah 46:13 states, "The word that the LORD spake to Jeremiah the prophet, how Nebuchadnezzar king of Babylon should come and smite the land of Egypt." This is further demonstrated by the flow of the chapter. Generally, the day of the Lord is the day when God no longer holds back His wrath but rather executes His vengeance on the wicked.
Prophetically, the main time of this wrath will be during the tribulation. It is during this time that men cry out, "For the great day of his wrath is come; and who shall be able to stand?" (Revelation 6:17). This time begins with the removal of the believers of this age in what is known as the rapture. 1 Thessalonians 5:2-3 states, "For yourselves know perfectly that the day of the Lord so cometh as a thief in the night. For when they shall say, Peace and safety; then sudden destruction cometh upon them, as travail upon a woman with child; and they shall not escape." When the believers are caught up to meet the Lord in the air (1 Thessalonians 4:17), the world will be taken by surprise as one is surprised by a thief breaking into a house at night. This is the beginning of the prophetic day of the Lord.
Most of the references to the day of the Lord (and to similar phrases like "that day" or "the great day') deal with the events of the tribulation. However, at least one passage expands the meaning of the day of the Lord. 2 Peter 3:10 states, "But the day of the Lord will come as a thief in the night; in the which 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." This destruction of the heaven and the earth is not mentioned in the book of Revelation until Revelation 20:11 states that "the earth and the heaven fled away; and there was found no place for them." Yet, this is not only after the time of the tribulation, it is also after the thousand year reign of Christ.
This has caused many to expand the day of the Lord to include the time from the rapture to the destruction of heaven and earth at the end of the millennium. However, this causes a problem in interpretation. The kingdom age is certainly a time when the Lord is in charge, but it is not generally considered a day of wrath and vengeance. Rather, it is a time of blessing and goodness. On the other hand, as we saw earlier, the most powerful idea associated with the day of the Lord is that of wrath. How can we reconcile the two concepts?
My answer is to return to the main meaning of the phrase. The day of the Lord is not a single calendar event but a description of God's dealings with the world. The day of the Lord is a day of judgment when God settles accounts. As such, Old Testament events could be described as the day of the Lord if they were a time of God's wrath being poured out on a nation. The tribulation is the primary day of the Lord in the Bible. It will be a time of "great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be" (Matthew 24:21). Therefore, most of the Bible references to the day of the Lord deal with the tribulation and it can be considered primarily the day of the Lord.
However, at the end of the thousand year reign, men will once again rebel against the rule of God and He will come upon them in sudden wrath. This will culminate in the destruction of heaven and earth as the elements melt in fervent heat (2 Peter 3:10). Because the day of the Lord is defined as a day of God's wrath, this too is the day of the Lord.
In this way, we can avoid calling the kingdom of peace on earth the day of the Lord. It may be cleaner and neater to some to simply block off a time period and call it the day of the Lord, but I think it is best to stay with the clear scriptural definition for the day of the Lord.