There exists among many Evangelical Protestants a dogma based on some passages in the Bible called millennialism which means a "thousand year reign." The basis for millennialism is found in the Book of Revelation.
Then I saw an angel come down from heaven, holding in his hand the key to the abyss and a heavy chain. He seized the dragon, the ancient serpent, which is the Devil or Satan, and tied it up for a thousand years and threw it into the abyss, which he locked over it and sealed, so that it could no longer lead the nations astray until the thousand years are completed. After this, it is to be released for a short time. Then I saw thrones; those who sat on them were entrusted with judgment. I also saw the souls of those who had been beheaded for their witness to Jesus and for the word of God, and who had not worshipped the beast or its image nor had accepted its mark on their foreheads or hands. They came to life and they reigned with Christ for a thousand years. The rest of the dead did not come to life until the thousand years were over. This is the first resurrection. Blessed and holy is the one who shares in the first resurrection. The second death has no power over these; they will be priests of God and of Christ, and they will reign with him for (the) thousand years. When the thousand years are completed, Satan will be released from his prison. He will go out to deceive the nations at the four corners of the earth, Gog and Magog, to gather them for battle; their number is like the sand of the sea. They invaded the breadth of the earth and surrounded the camp of the holy ones and the beloved city. But fire came down from heaven and consumed them. The Devil who had led them astray was thrown into the pool of fire and sulfur, where the beast and the false prophet were. There they will be tormented day and night forever and ever. Next I saw a large white throne and the one who was sitting on it. The earth and the sky fled from his presence and there was no place for them. I saw the dead, the great and the lowly, standing before the throne, and scrolls were opened. Then another scroll was opened, the book of life. The dead were judged according to their deeds, by what was written in the scrolls. The sea gave up its dead; then Death and Hades gave up their dead. All the dead were judged according to their deeds. Then Death and Hades were thrown into the pool of fire. (This pool of fire is the second death. ) Anyone whose name was not found written in the book of life was thrown into the pool of fire.
The Magisterium of the Church has never commented on a thousand year reign of Christ. Rather, as is already clear from what is covered in these notes, the Church does not see the Second Coming of Christ at any other time than at the general judgment of all men and women which is the same as the resurrection of the dead followed by definitive reward or punishment for souls.
The Church interprets the expression "a thousand years" not literally but according to the literature in which it appears--prophetic and apocalyptic. In apocalyptic literature, a thousand years would simply indicate a long period of time, in this case, the time period before the Second Coming of Christ. Apocalyptic literature is not to be taken literally.