Ben asks,
“If you are saying that the Day of the Lord and the Day of Christ are the same event, does that mean that the Day of the Lord is the rapture?“
The “Day of the Lord (or Christ)” commences with the deliverance of the righteous by the rapture followed by God’s wrath against the ungodly who remain on the earth.
But a few comments should be made about variant descriptions of our Lord’s Return described most commonly as “The Day of the Lord.”
First, Paul and other New Testament writers commonly used “Lord” and “Christ” interchangeably in many Christological contexts. Not to mention that they frequently combine the terms throughout the New Testament (e.g. 14 times in the Thessalonians),
“Paul and Silvanus and Timothy, To the church of the Thessalonians in God our Father and the Lord Jesus Christ: Grace to you and peace from God the Father and the Lord Jesus Christ.” – 2Th 1:1-2
Second, Paul has the freedom to extend the traditional term “Day of the Lord” to “Day of our Lord Jesus Christ” because his Christology teaches him that the Lord is Jesus Christ. In the Old Testament era, Christ was not revealed. In the New Testament apostolic era the apostles have learned that the “Day of the Lord” is a time when Christ will be magnified and vindicated; hence the “Day of Christ” or “Day of our Lord Jesus Christ.”
Third, When Paul places an emphasis on our sanctification or the deliverance of the righteous at Christ’s Return he has used the term “The Day of Christ” or a variant of it; and when he wants to place emphasis on the judgment aspect of Christ’s Return he often employs “The Day of the Lord.” But it would be a mistake to confuse these emphases on different aspects of the Coming of our Lord by disconnecting the rapture from its immediate subsequent wrath of God (They are back-to-back events).
Fourth, to begin to appreciate the freedom that the New Testament writers had with the traditional term “Day of the Lord” here is a good sampling of variants:
Pauline: “the day of Christ”; “the day of Jesus Christ”; “the day of our Lord Jesus Christ”; “the day of the Lord”; “the day”; “that day”; “the day of wrath.” Non-Pauline: “the days of the Son of Man (Luke 17:22, Noah); “the great day” (Rev. 6.17); “the day of visitation” (1 Peter 2:12); “the last day” (John 6); “the day of judgment” (1 John 4:17)