'Day' in the Bible

when he comes to be glorified among his saints and admired on that day among all who have believed -- and you did in fact believe our testimony.

not to be easily shaken from your composure or disturbed by any kind of spirit or message or letter allegedly from us, to the effect that the day of the Lord is already here.

Let no one deceive you in any way. For that day will not arrive until the rebellion comes and the man of lawlessness is revealed, the son of destruction.

and we did not eat anyone's food without paying. Instead, in toil and drudgery we worked night and day in order not to burden any of you.