The theme of the Lord's day continues in 2 Thessalonians. So Paul
warned the Thessalonian church about the problem that they had in the
relation to the second coming. And he also encouraged the church about
the strong faith and love that continued growing in the days of trial.

As you can tell from this letter, the day of the Lord is also called
the day of God's righteous judgment (1:5). The keyword that we have to
pay attention to in here is "righteous". Because from this keyword, it
is clear that the judgement on the Lord's day is not just about the
evil ones but also the righteous. So the trouble will be given to
those who suffered the righteous as the reward (1:6-7). And to those
who is righteous and troubled, God will give them rest. Paul and the
Thessalonian church were the latter and were suffered while they wait
for the just judgement to come (1:4). But they had "righteous
judgement" as good hope and everlasting consolation (2:16). So their
faith grew stronger and became more firm in the days of trial (1:3).

The day of the Lord was a hope for the righteous. Than what was it for
the people who persecuted them (1:6)? As Paul described chapter 2,
before Jesus Christ appears with the mighty angels (1:7), the man of
sin (2:3-12), who is also called the son of perdition (2:3) will
appear and declare themselves as god (2:4). They delude and deceive
the people (2:9-10). And those who did not believe in Christ (2:10-11)
will perish. Because they believed not the the truth but had pleasure
in unrighteousness (2:12). So for those people, the day of the Lord is
the day of punishment of eternal destruction (1:9) in contrast to the
eternal comfort (2:16).

But the man of sin and the son of perdition and his believers were not
the only problem. But as Paul warned the church in chapter 2, some
people tried to deceive the church and made false claim about the Days
of the Lord (2:2-3). So that the people will be shaken and troubled
with words and spirits. They sent letters to the church as if they
were sent from Paul. And this is why Paul wrote about "the mark" that
he wrote on every letter that he sent to the churches (3:17).

But the man of sin and fake Paul were not the only people who were
causing problems in the relation to the Lord's day. But there were
some people in the church who stopped working and lived lazy lives as
busybodies to wait for the Lord's day (3:6-15). So Paul instructed the
church to commanded them to work quietly and to become financially
independent. But he is also telling them to warn the lazy people as
brothers and not as enemies (3:15).

So we can conclude that three kinds of people were the cause of the
trouble in the days of trial. One is the man of sin, son of perdition
(2:3, 8). Second are the fake Paul"s" (2:2-3), and the third are the
brothers that were living lazy lives (3:5). So Paul taught the church
on how to deal with those people and he also encouraged them that God
will guard them from the evil ones (3:2-3). From what Paul wrote about
the strong hope, faith and love that the Thessalonian church had, it
is clear that God protected them from the wicked and evil men (1:3-4).
So Paul exhorted them to keep their faith even stronger and to
increase the love among them (1:11-12, 2:16-17). These are the problem
and solution about the Day of the Lord that Paul wrote in 2
Thessalonians.