I like to see more of the context. Let's consider 1 Thessalonians 5:1-7
Now as to the times and the epochs, brethren, you have no need of anything to be written to you. For you yourselves know full well that the day of the Lord will come just like a thief in the night. While they are saying, “Peace and safety!” then destruction will come upon them suddenly like labor pains upon a woman with child, and they will not escape. But you, brethren, are not in darkness, that the day would overtake you like a thief; for you are all sons of light and sons of day. We are not of night nor of darkness; so then let us not sleep as others do, but let us be alert and sober. For those who sleep do their sleeping at night, and those who get drunk get drunk at night. But since we are of the day, let us be sober, having put on the breastplate of faith and love, and as a helmet, the hope of salvation. For God has not destined us for wrath, but for obtaining salvation through our Lord Jesus Christ, who died for us, so that whether we are awake or asleep, we will live together with Him. Therefore encourage one another and build up one another, just as you also are doing.
I highlighted two phrases in the text above in order to clarify the dual nature of the DOL. The day does not affect everyone the same way.
First group:
They
Day is a surprise
destruction comes suddenly
like a thief in the night
they will not escape
Second Group:
You
Day is not a surprise
Not overtake you like a thief.
Not destined for wrath
Obtaining salvation
Conclusion:
From this passage we can see that the DOL is NOT a quick, sudden, eschaton, but an extended period of time. The day lasts at least long enough for those who walk in the light to see what is happening and act accordingly. The day comes "suddenly" for some but not for others. For some, the day is unforeseen, and abrupt, while for others the day is foreseen and it comes slow enough that those walking in the light can see it and recognize it.
The day will experience destruction for some, but not for others. The day will witness wrath for some but not for others. Some will not escape the destruction but others will escape.
Jesus repeats this idea in the book of Revelation:
Revelation 3:2-3
Wake up, and strengthen the things that remain, which were about to die; for I have not found your deeds completed in the sight of My God. So remember what you have received and heard; and keep it, and repent. Therefore if you do not wake up, I will come like a thief, and you will not know at what hour I will come to you.
Jesus, speaking to the church in Sardis, exhorts them to wake up and if they don't wake up, he will come like a thief, and they will not know at what hour he will come. This implies that if the church of Sardis wakes up, Jesus' coming will not overtake them like a thief; they will be sober and ready for his return. Just as Paul said, Jesus' coming will be like a thief for those who are asleep, but not for others who are awake, they will know the hour he is coming.
The Day of the Lord is NOT a sudden, quick, climactic, surprise, eschaton as we see above. For those that are awake, alert, walking in the light both the Day of the Lord and the Second Advent will be anticipated, foreseen, and gradual. It only comes suddenly for those whom it remains "unforeseen", for those walking in the darkness and not in the light.