'Day' in the Bible

when He comes to be glorified in His saints on that day [that is, glorified through the changed lives of those who have accepted Him as Savior and have been set apart for His purpose], and to be marveled at among all who have believed, because our testimony to you was believed and trusted [and confirmed in your lives].

not to be quickly unsettled or alarmed either by a [so-called prophetic revelation of a] spirit or a message or a letter [alleged to be] from us, to the effect that the day of the Lord has [already] come.

Let no one in any way deceive or entrap you, for that day will not come unless the apostasy comes first [that is, the great rebellion, the abandonment of the faith by professed Christians], and the man of lawlessness is revealed, the son of destruction [the Antichrist, the one who is destined to be destroyed],

nor did we eat anyone’s bread without paying for it, but with labor and hardship we worked night and day [to pay our own way] so that we would not be a financial burden on any of you [for our support];