It was a common denominator among the prophets—including the prophetic visions of Christian prophets like Peter—that the time difference between near-term and far-term fulfillment was difficult to discern.
It seems clear the first century church expected Jesus to return within their lifetime—in fact, according to the Gospel of John, a rumor had started that John would not die before Jesus’s second advent. When John did die, close to the turn of the century, it became necessary to attach an epilogue to John’s gospel to discredit that rumor, and to allay people’s fears for the future.
Of the two recorded visions God gave Peter, fulfillment of the first (found in Acts 10) happened within moments of Peter receiving it. Fulfillment of the second, recorded in Peter’s second letter, has still not come.
New Heavens and a New Earth
Usually, when people think about endtime scenarios, they turn to the book of Revelation, or to Daniel, or maybe (if they are really in the know) Zechariah. But not that many people know the Apostle Peter also had a heavily eschatological message.
But the day of the Lord will come like a thief, and then
the heavens will pass away with a loud noise, and the elements will be dissolved with fire, and the earth and everything that is done on it will be disclosed.
Since all these things are to be dissolved in this way, what sort of persons ought you to be in leading lives of holiness and godliness, waiting for and hastening the coming of the day of God, because of which the heavens will be set ablaze and dissolved, and the elements will melt with fire? But, in accordance with his promise, we wait for new heavens and a new earth, where righteousness is at home.
2 Peter 3:10-13 (NRSV)
This had to have been a hair-raising vision for Peter, the entire earth engulfed in flames, the heavens literally melting, even the very air scorched.
Christians who are nuclear scientists who have considered Peter’s oracle have seen a description of a nuclear explosion in these verses. The present heavens and earth will be completely destroyed, even the elements will be undone, the very structure—in Greek stoichea, which is translated something orderly in arrangement, element, principle, rudiment—of the universe will dissolve, atom pried from atom, so that nothing is left. This would complete the predictions of the Hebrew prophets concerning the Day of the Lord judgment.
And out of that immense conflagration would arise a new heavens and a new earth. What sort of persons ought you to be, then? asked Peter, Since all these things are to be dissolved in this way? Ought it not be in leading lives of holiness and godliness, waiting for and even hastening the coming of the Day of God?
Peter was not proposing a return to the legalistic observances of the Pharisees, though these spiritual leaders were held in great esteem by the people. Rather than outward shows of piety, Peter was instead pointing to two traits God had called of God’s people since the days of the wilderness wanderings, godliness and holiness.
Godliness means to be conformed to God’s character, to embrace God’s perspective, to approve and live by God’s values, and to endorse God’s priorities. To be godly is to be like God, so filled with God’s life, love, and Spirit as to be a living image of who God is.
To be holy is to be set apart, to live entirely in the domain of the sacred, so that all we do and say, all we touch, all whom we relate with becomes sacred, having entered the holy space we occupy. To be holy in the way God is holy, in the way Jesus was holy, is to be so complete, so mature (spiritually and emotionally), that we bring wholeness and health, beauty and love, grace and peace into every place and every person we are with.
The Day of God
Since all these things are to be dissolved in this way, what sort of persons ought you to be in leading lives of holiness and godliness, waiting for and hastening the coming of the day of God, because of which the heavens will be set ablaze and dissolved, and the elements will melt with fire? But, in accordance with his promise, we wait for new heavens and a new earth, where righteousness is at home.
2 Peter 3:12-13 (NRSV)
Those who study eschatology (the study of the end of time) say The Day of God is not the same as The Day of the Lord. The Day of God is what believers wait for and can even, it seems, by godly living, speed up in its coming.
God will call forth a completely new world, indeed, it seems, a whole new universe, if that is what is meant by a “new heavens,” to rise up out of the ashes of the old, much like a new earth rose from the waters of the cleansing Flood.
Evidently, somewhere in between the Day of the Lord coming like a thief and the heavens and earth passing away will come other significant events referred to in a number of Hebrew prophets, the gospels, Paul’s letters, and the book of Revelation. These events include a time of tribulation and what some refer to as the Millennium, a Latin word meaning “thousand years,” which is found in the Bible only in the first six verses of Revelation 20.
Whatever this Millennium will be (or, as some would have it, has been) what is described in scripture is a thousand‑year reign of righteousness of the Lord Jesus Christ on earth, judging evil with a rod of iron so that righteousness will be the preferred lifestyle. It is all to happen at the very end of human history, but before God’s final judgement, the creation of a new heavens and earth, and the entrance of believers into the eternal, pure, glorified state Paul spoke of in 1 Corinthians 15.

What is the Millennium?
Sincere believers hotly disagree on this one.
Some say that there is no millennium at all, the millennium prophecies are really symbolic of the church age, which is right now. They are known as amillennialists, “a” means “no,” “no millennium”
Postmillennialists think a millennium age will occur first, then Jesus will physically come back at the close of the millennium; “post” means after.
Premillennialists think Jesus will physically return before the millennium, when he will literally set up his kingdom on earth; “pre” means before.
Each of these theories has proof texts, smart and Spirit-filled scholars to argue their case, and canny arguments in their favor.
It is no secret the first century church favored the premillennial view. They knew that all throughout the history of the Jewish people, and documented in their prophets, the Lord had literally (if in often surprising and unexpected ways) and accurately fulfilled the predictions God had made. It seemed obvious that God would again literally, concretely fulfill the Spirit-produced prophecies the Lord had inspired concerning the end of time.
It was not until the fourth century, when life had stabilized for Christians, and Constantine had legitimized the Christian faith, that amillennialist and postmillennialist views began to gain traction.
However, the truth is, all believers today do agree on the broad brush strokes. Everyone agrees Jesus is coming back for his own. Everyone agrees that at some point our earth will be dissolved (everyone believes that, by the way, and we know it is going to happen no later than in about 5.5 billion years, when the sun goes supernova).
And every Christian believes our destiny is to be with God for all eternity in a glorified state.
[Supernova, Color rendering is done by by Aladin-software (2000A&AS..143…33B.) | By Fabian RRRR – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19318800