Peter says the day of the Lord will come “like a thief.” He describes the heavens passing away with a roar and the heavenly bodies being burned up and dissolved, and the earth and its works being exposed. The emphasis is on sudden arrival and cosmic upheaval. See 2 Peter 3:10.
In 2 Peter 3:8–10 the writer answers the complaint that the promised “day” seems delayed. He tells the beloved community to remember that God’s sense of time does not match human calendars, so what looks long to them is not necessarily “slow” to him. The delay is framed as patience, aimed at giving people time to turn around. These verses sit in the letter’s closing argument about the future and how the community should live while waiting. Just before this, the writer reports that some mock the idea of the Lord’s coming and use the apparent stability of the world to dismiss the promise (3:3–7).
These verses answer a specific complaint: the promised “day of the Lord” seems late. The writer’s main move is to challenge human assumptions about timing. What seems like a long delay to people does not mean the Lord is failing to act (explicit: verse 8–9). The delay is interpreted as patience with a purpose.
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with 2 Peter 3:10, then read the surrounding section so the answer stays connected to the passage's flow.
10But the day of the Lord will come as a thief in the night; in which the heavens will pass away with a great noise, and the elements will be dissolved with fervent heat, and the earth and the works that are in it will be burned up.