Paul had previously taught this church about the day of the Lord ( 1 Thessalonians 5:2). Jesus had also taught His disciples about it (cf. Matthew 24:44; Mark 13; Luke 21). They had taught about the chronological periods ("times," Gr. chronos, an extended period) and the major features of those periods ("epochs," Gr. chairos, a definite period) that lay ahead in the future. These words may describe the end times from these two perspectives (cf. Acts 1:7; Acts 3:19-21). [1] But probably they mean virtually the same thing (cf. Daniel 2:21; Daniel 7:12; Acts 1:7). [2][source]
". . . the phrase may have been a conventional doublet, like our own "times and seasons," with no particular emphasis on a difference between the two nouns." [3][source]
"The day of the Lord" usually refers in Scripture to a time in history characterized by God"s working in the world in direct, dramatic ways. [4] It contrasts with the day of man in which affairs appear to be proceeding without divine intervention. The eschatological day of the Lord prophesied in the Old Testament begins with the Tribulation and continues through the Millennium (cf. Isaiah 13:9-11; Joel 2:28-32; Zephaniah 1:14-18; Zephaniah 3:14-15; et al.). It contains both judgment (in the Tribulation) and blessing (in the Millennium). People living on the earth when it begins (i.e, unbelievers, since Christians will be with the Lord in heaven immediately following the Rapture) will not expect it. [source][source][source]
"The meaning [3]3 would be not that the Day will come as unheralded as a thief, but that it will surprise people ..." [6][source]
"By using "day of the Lord" terminology to describe the great tribulation, Christ included the tribulation within the day of the Lord (cf. Matthew 24:21 with Jeremiah 30:7; Daniel 12:1; Joel 2:2). This time of trial at the outset of the earthly day of the Lord will thus not be brief, but comparable to a woman"s labor before giving birth to a child ( Isaiah 13:8; Isaiah 26:17-19; Isaiah 66:7 ff.; Jeremiah 30:7-8; Micah 4:9-10; Matthew 24:8; 1 Thessalonians 5:3)." [7][source]
The phrase "the day of the Lord" also refers to the Second Coming of Christ (cf. Joel 3:9-16; Zechariah 14:1-5; Revelation 16:12-16; Revelation 19:11-21); it includes that event between the Tribulation and the Millennium. Thus Scripture uses the term in a broad sense (the Tribulation and the Millennium) and a narrow sense (the return of Christ). [source][source][source]
"Just as the word "day" in Genesis 1:5 has both a broad sense (a24-hour day-"And the evening and the morning were the first day") and a narrow sense (the light part of a24-hour day in contrast with the darkness part-"And God called the light Day, and the darkness he called Night")-so the expression "the Day of the Lord" has both a broad and a narrow sense in relationship to the future." [8][source]
Some posttribulationists say the day of the Lord here refers only to the second coming of Christ. [9] However in the context this day will be a time when God will pour out His wrath on unbelievers ( 1 Thessalonians 5:3-9). While this could refer to the judgments that will take place at Christ"s second coming, it seems more likely to refer to the judgments of the Tribulation (cf. Matthew 24:5-28; Revelation 6:16-17). [10] Gundry contended that the day of the Lord begins after the Tribulation but before Armageddon. [11] However this means that none of the judgments before Armageddon are judgments of the day of the Lord, a conclusion that few interpreters, posttribulational as well as pretribulational, have accepted. [3][source]
"The only way to hold that this meeting with Christ in the air is an imminent prospect is to see it as simultaneous with the beginning of the divine judgment against earth. Only if the rapture coincides with the beginning of the day of the Lord can both be imminent and the salvation of those in Christ coincide with the coming of wrath to the rest ( 1 Thessalonians 5:9) ... [source][source][source]
"Were either the rapture or the day of the Lord to precede the other, one or the other would cease to be an imminent prospect to which the "thief in the night" and related expressions ( 1 Thessalonians 1:10; 1 Thessalonians 4:15; 1 Thessalonians 4:17) are inappropriate. That both are any-moment possibilities is why Paul can talk about these two in successive paragraphs. This is how the Lord"s personal coming as well as the "day"s" coming can be compared to a thief ([3]0 2 Peter 3:4; 2 Peter 3:10; Revelation 3:3; Revelation 3:11; Revelation 16:15)." [14][source]