The Day Of The Lord
Principles of grammar and similar constructions elsewhere (cf. Notes) show that the two phenomena are conceived of as within the day of the Lord, not prior to it. The day of the Lord is not yet present because these two conspicuous phenomena that will be distinguishing characteristics of that day have not yet surfaced. The issue involved in Paul’s correction of the false information to which the readers have been exposed is not the future coming of the day of the Lord; it is rather the current presence or nonpresence of that day at the time he writes and they read his words.
A major issue in understanding this verse is the function of the adverb prōton (GK 4754; NASB, “first”; NIV, “until”) in the first half of the protasis. Commonly, the sense assumed is that the arrival of the “rebellion” (NASB, “apostasy”) and the revealing of “the man of lawlessness” will precede the day of the Lord. This understanding is faulty. “First” indicates that the arrival of the apostasy will precede the revealing of “the man of lawlessness,” but not the day of the Lord (cf. Notes). Both of these events fall within the day of the Lord and will be easily recognizable signs to those on earth when they happen.