'Day' in the Bible

whenever he should come to be glorified on that day by his saints and to be marveled at by all who believe, because our testimony was believed among you,

that you not be easily shaken from your composure, nor be troubled either by a spirit or by a message or by a letter {alleged to be from us}, to the effect that the day of the Lord has arrived.

Do not let anyone deceive you in any way, for [that day will not come] unless the rebellion comes first, and the man of lawlessness is revealed, the son of destruction,

nor did we eat bread from anyone without paying, but with toil and labor, [we were] working night and day in order not to be a burden to any of you,