It is something that at some point in time *has already happened.* You cannot use the form of the word "come" to indicate that a single day continues on forever!
If this supposed "coming" of Christ took place, as was proposed, at some point in the past, then at some point it has to remain in the past, and no longer continue into *our* present! Since it references a literal 24 hour day, that day took place in the past and was completed on the same day in the minds of those who claimed it.
Allow me to re-phrase the actual definition of the "Perfect Tense" from the Greek Grammar sites...
... keeping in mind that the
false conveyors were [or even 'potentially' could be]
purporting that ____ "IS ALREADY HERE / IS PRESENT [*PERFECT INDICATIVE]" (v.2)... and Paul is saying for them not to believe such a claim...
[quoting definition]
Perfect Tense -
"ACTION COMPLETED at a SPECIFIC POINT of TIME in PAST (●) with results CONTINUING into the PRESENT (▬►). In certain contexts the results are PERMANENT."
"the perfect tense... emphasizes the present, or ongoing result of a completed action."
[end quoting]
... so if they were purporting something "IS ALREADY HERE / HAS ALREADY ARRIVED / IS PRESENT [PERFECT INDICATIVE]"... then its "results" are "CONTINUING into the PRESENT" (meaning, "whatever it was"... took place/was completed at a SPECIFIC POINT of time in the PAST, and its results were CONTINUING into the PRESENT"
[unless we can think of something that would have intervened to "CHANGE THAT STATUS" like, introducing further info that changes the "results" from what one could call "PERMANENT" to instead be considered "NOT PERMANENT"
after all, like "Jesus said His kingdom would be pretty BRIEF, you recall..."... but, as I see it, that'd be a notion I would think would be rejected from those CONVEYING the falsehood if the thing they claimed "IS ALREADY HERE / HAS ALREADY ARRIVED" was
His Second Coming and the Rapture event (even tho there was
ZERO EVIDENCE anywhere in sight, for such a thing to have convinced the Thessalonians WAS TRUE and cause for "troubled in mind / shaken" status for
their part...)]
... I'm just not seeing it... I remain unconvinced of your viewpoint, based on the actual text Paul conveyed
especially in v.2 (about the false conveyors' purportings... I do NOT believe the text itself is getting across the point that the false conveyors were saying "CHRIST has returned, and the RAPTURE has taken place" [
*zero evidence* is blaring loudly to the Thessalonians right about now... the ppl who "KNOW PERFECTLY" the manner of "the DOTL's *ARRIVAL* (which Jesus also spoke of), according to the previous epistle...])