The phrase "Day of the Lord," is used throughout Scripture and is vital to the believer's understanding of future events. A review of its use in the Old Testament reveals that it was often employed by the prophets to designate both near historical and future eschatological events. Also, the New Testament writers use of the phrase, "Day of the Lord," was based on their understanding of the Old Testament prophets. Mayhue points out, "The New Testament writers picked up on the eschatological use and applied the phrase both to the judgment which will climax the Tribulation period and the judgment which will usher in the new earth." Thus, a clear understanding of "Day of the Lord" is necessary for a proper perspective on God's plan for the future. The phrase appears nineteen times in the Old Testament and is used by six minor (Joel, Amos, Obad., Zeph., Zech. and Mal.) and two major prophets (Ezek. and Isa.). In the New Testament, "Day of the Lord" appears in four uncontested passages (Acts 2:20, 1 Thess. 5:2, 2 Thess. 2:2, and 2 Peter 3:10).

According to Walvoord, "the Day of the Lord refers to any special period where God intervenes supernaturally, bringing judgment on the world." Benware defines the "Day of the Lord" as "A phrase used in the Bible to emphasize special interventions of God in human history, including the future time when He will intervene to judge the nations, discipline Israel, and establish His rule in the Messianic Kingdom." The Book of Joel provides a fascinating perspective on "the Day of the Lord". Joel employs the term five times (1:15, 2:1, 2:11,2:31 and 3:14), and while he used the phrase to describe a crisis involving an infestation of locusts that ruined crops and resulted in starvation and destruction (Joel 1:15-20), he appears also to include the coming invasion by the Assyrian armies as part and parcel of this day of judgment (Joel 2:1-11). The immediate aspect of Joel's prophetic warning was an appeal to Israel to return to the Lord. (2:12-14). However, he telescopes his description of "the Day of the Lord" to include a universal, eschatological application (3:14-16) which climaxes his prophecy with a description of international judgment in the presence of God (3:2, 3:14) and appears to anticipate a number of New Testament passages including Matt. 13:41-43, 49-50; 24:37-41; 25:31-46; 2Thess. 1:9 and Rev. 14:17-20.

"Day of the Lord," then, can refer to several events in God's prophetic plan, depending on the context in which it is used. Walvoord, for example, in his eschatological application of "Day of the Lord" holds that it "will begin as a time period at the Rapture, but its major events will not begin immediately. The ten-nation kingdom must be formed in the final seven years before the Second Coming will begin. . . . Once the Day of the Lord begins . . . there will be obvious signs that they are in the Day of the Lord and in the period leading up to the Second Coming just as there will be obvious evidences that the millennial kingdom has begun after the Second Coming."

The question of when the Day of the Lord begins is a watershed issue which impacts whether the Rapture occurs before or after the Tribulation.. For example, in 1 Thess. 4:13-18 Paul attempted to alleviate the concern of the Thessalonians who feared that deceased believers might not share in the Kingdom. He addresses the issue as something about which they were uninformed in contrast to how he discusses the Day of the Lord in 5:1-11. Obviously Paul's readers were well informed concerning the Day of the Lord, partly from his own teaching, but also from their acquaintance with the Old Testament usage of the phrase. Posttribulationalists view the ease with which Paul moves from his discussion of the Rapture in 4:13-18 to the discussion of parousia in 5:1-11 as evidence that the events occur simultaneously and are not separated by a seven year tribulation period. They see Paul's use of de (the first Greek word in 5:1), a simple connective with only a slight contrastive sense, as indication of a close connection between the two passages. They reason that since the Day of the Lord will not begin until the Second Coming, the Rapture will take place then as well.

Pretribulationists respond by pointing out that while Paul uses de, it is coupled with peri forming the phrase peri de, used elsewhere in Paul's writings to denote a new and contrasting subject (e.g. 1 Cor. 7:1, 25; 8:1; 12:1; 16:1, 12; and I Thess. 4:9 and 5:1). Thus, the pretribulational perspective on the passage is strongly supported exegetically, separating the Rapture from the Day of the Lord. Most Pretribulationists, then, hold that the Day of the Lord begins at the start of the Tribulation. Ryrie holds that if such is not the case, Posttribulationalists must deal with the following questions:

1. How can the Day of the Lord not begin with the Tribulation or any part of it and yet begin with the judgments of Armageddon?
2. How can the final conflict at the end of the Tribulation be condensed into a single battle of short enough duration that the church can be raptured before it starts (in order to escape the wrath) and yet turn around and immediately accompany Christ on His return to earth at the conclusion of what would have to be a very brief battle?
3. Does protection from the wrath poured out on unbelievers really include exemption from the fallout effects of the actions of those unbelievers on whom the wrath is poured out? It does not today. Why should it in the future?
4. How does compacting the wrath judgments at the end of the Tribulation solve the problem that equally severe judgments seem to take place earlier in the Tribulation and fall on believers as well as unbelievers?
5. What is the normal interpretation of the aorist in Rev. 6:17? Does it not indicate that the wrath has already been poured out and did not begin with the sixth seal?
6. Does not the use of the phrase peri de in 1 Thess. 5:1 indicate that the Rapture is really not a part of the Day of the Lord at the end of the Tribulation?

He concludes that only Pretribulationism harmoniously fits the Scriptural evidence and answers these questions satisfactorily.

While most premillennial dispensationalists see the Day of the Lord as beginning at the pretributional rapture and extending on through the millennium, others, such as Mayhue, see two periods of the Day of the Lord yet to be fulfilled on earth: (1) the judgment which climaxes the tribulation period (2 Thess. 2:2; Rev. 16-18); and the consummating judgment of this earth which ushers in the new earth (2 Pet. 3:10-13; Rev. 20:7-21:1). The suggestion is that the Day of the Lord will occur only at the end of the Tribulation and at the end of the millennium rather than throughout the duration of these end-time periods.