From the OSB:
The Orthodox understanding of the second coming of Christ is clear: The Lord Jesus Christ truly will return. His second advent is not a myth nor an empty promise, nor is it a metaphor. In fact, each time the Divine Liturgy is celebrated, the priest makes a proclamation to the Father that reveals how the Church responds not only to the second coming of Christ, but to all of His work.
Remembering this saving commandment [Jesus’ command to eat His flesh and drink His blood] and all that has been done for us—the Cross, the Tomb, the Resurrection on the third day, the Ascension into heaven, the sitting at the right hand, and the second and glorious coming—we offer You Your own, from what is Your own, on behalf of all and for all.
Orthodox Christians also believe the New Testament revelation of the second coming of Christ is meant to stimulate our preparation for it, not our speculation about it. This explains the relative simplicity with which the Nicene Creed, the most universal confession of faith in all of Christendom, addresses Christ’s return: “He . . . will come again, with glory, to judge the living and the dead, whose Kingdom shall have no end.” The emphasis of historic Orthodoxy is that Jesus will come again, not when He will come again.
Thus, St. Paul writes, “denying ungodliness and worldly lusts, we should live soberly, righteously, and godly in the present age, looking for the blessed hope and glorious appearing of our great God and Savior Jesus Christ, who gave Himself for us, that He might redeem us from every lawless deed and purify for Himself His own special people, zealous for good works” (Tts 2:12–14).
There are signs of Christ’s coming, to be sure. Jesus prophesied many events that would take place in the world prior to His return (Mt 24; Lk 21:7–36). But even these Gospel passages close with Jesus’ exhortation to virtue, righteousness, and preparation for the Judgment. Christ and His apostles issue severe warnings, implicit and explicit, against second-guessing the time of His coming (Mt 24:3–8, 36, 43, 44, 50; Lk 21:7–9, 34; Acts 1:7; 1Th 5:1–3; 2Pt 3:8–10).
Much of modern Christendom has succumbed to divisive speculation regarding Christ’s return. We are divided into premillennial, postmillennial, and amillennial camps. Breaking it down even further, there are pre-tribulation, mid-tribulation, and post-tribulation adherents. Christians part ways and new denominations spring up around interpretations of events that have not yet even come to pass!
Throughout history the Orthodox Church has steadfastly insisted on the reality of the second coming of Christ as a settled belief, but has always granted liberty on the question of when it will occur. In the last chapter of Revelation, Jesus speaks the words, “I am coming quickly,” three different times (22:7, 12, 20). His coming will occur on a day and at an hour when it is not expected. The apostle John, the author of Revelation, concludes his book with a warning:
For I testify to everyone who hears the words of the prophecy of this book: If anyone adds to these things, God will add to him the plagues that are written in this book; and if anyone takes away from the words of the book of this prophecy, God shall take away his part from the Book of Life, from the holy city, and from the things which are written in this book (Rev 22:18, 19).
To confess the return of Christ is to stand squarely within the apostolic tradition. To add “when” to the promise of His coming is warned against in the Scriptures. As members of the Bride of Christ, let us attend instead to being ready.