All matters of religion appear difficult to most people because they are of a spiritual nature; but even more difficult is the topic of the "last things," for they have to do with future realities "that are not seen" (Heb. 11:1; Jn. 3:10-12), that only faith can "see," examine, and make real.
The Jewish people were the beloved people of God and yet they were not satisfied with their present life in this world. All the great personalities of the Old Testament lived with hope for the future, for the fulfillment of the promises made by God to Abraham. Their main hope was the hope of the coming of the Messiah Savior, who would bring days of divine blessings for the Jewish people and for the whole world (cf. Lk. 2:25; 24:21). And they expected this to happen at some future date, in the last days of history "in the last days," "in that day," "in the day of the Lord" as this time was often referred to.
For Christian faith these ultimate and final events have a dual character. When we look upon them from the perspective of the Old Testament, the "last things" are realized in the person of Jesus Christ who is the expected Messiah. The entire history of Israel and of the other nations had as its goal the coming of Christ and the establishment of the Church. All things in the history of Israel were types (typos or signs) that became realities in the person of Christ and in the life of the Church (Jn. 3:14-16; 1 Cor. 10:11; Heb. 10:1; 1 Pet. 1:10-12). Indeed, all the hopes of Israel were realized in the person of Christ and in the life of the Church. With the movement of St. John the Baptist, and especially with the life, Cross and Resurrection of Christ, the eschata, the new age began; the kingdom of God was inaugurated. But from the perspective of the Church, the "last things" in themselves are expected to take place mainly in the future, at the glorious Parousia, that is, at the Second Coming, the future appearance of the Lord in glory (Mt. 24:30; 1 Thess. 1:10; 4:16-18; 1 Tim. 6:14-15). It is then and there that we will have the fullness of the eternal kingdom of God; when we will experience a perfect koinonia communion with God in Christ, as our soul yearns it. This is the height and the depth of our faith and the wealth of glory that awaits us (Eph. 1:17-18).
There is one world and its history is unified: from creation to the Incarnation, and through the Church to the Parousia, to the fullness of the kingdom of God. The Church lives between the first and the second coming of our Lord.
The Parousia and the End of the Age
The Parousia will take place in the final days, at the last stage of present history. With the Parousia we will also have the end of the present world and the beginning of the new one, the "new creation" (Rev. 21:5). From the old will come the new. This is the goal of the world, its perfection, its renewal and recapitulation in Christ. Thus the Parousia, the end and the goal of the world coincide.
The Parousia and the end of the world were a main concern in the days of the earthly life of Christ. Christ often pointed to the future for the consummation of all. He especially pointed to His future coming as the Son of Man, as the judge of the world (Mt. 16:27; 25:31; 26:64 Mk. 16:62; Jn. 5:28). The early Church lived with the expectation of His Parousia. A few days before His death, the disciples asked Christ:
"When will this be, and what will be the sign of your coming and of the close of the age?" (Mt. 24:3). The first Christians lived with the hope of the Parousia, especially in view of the difficult persecutions in the early centuries, and they expected it to occur soon (Mt. 24:3-6, 34; Rom. 13:11; 1 Cor. 7:25-31; 1 Thess. 5:1-11; 2 Thess. 3:3-16; Phil. 4:5).
The Parousia and the Mystery of Christ
Belief in the Parousia of Christ completes the faith in the person of Christ and the mystery of the divine plan of salvation. With the ultimate event of the Parousia we have the complete truth about Christ and His work. The work of salvation is the work of God in Christ. It began with the Incarnation, the Cross, and the Resurrection, and is in motion towards its ultimate goal. The crucified and resurrected Christ is already the Lord. He has received every authority in heaven and on earth (Mt. 28:18-20), and invisibly, in the Holy Spirit, He reigns through the Church and guides the world toward the end the perfection of the kingdom of God. The Parousia of Christ and our being gathered together with Him will be the final act of the divine plan for our salvation. With the Parousia the works of Satan, namely sin and death, will be completely destroyed. With the resurrection of the dead the kingdom of God will be perfected and the life of eternal blessedness will begin. This is the purpose of God's divine plan for our salvation. This is what the faithful anticipate.
The Time of the Parousia
We know well that the Lord will come again in glory (2 Thess. 2:2; 1 Thess. 4:11-17). The Church confesses: "He will come again in glory whose kingdom will have no end." Christ gave us certain signs which will precede the Parousia (cf. Mt. 24 and 25). But these were given mainly to keep us vigilant in life. No one knows the precise day and hour of the coming of the Lord (Mk. 13:32; Acts 1:7).
At that time many curious people were making academic inquiries, as some do now, about the precise day of the Parousia. Some lost their patience and began to have doubts about the Parousia and the resurrection of the dead. Others believed that the Parousia had already come (cf. 1 Cor. 15:12; 1 Thess. 2:1-2). The Apostles, however, made it their purpose to assure us that the Second Coming of Christ as well as the resurrection of all the dead will take place, but in their own time (1 Cor. 15:23; 2 Pet. 3:8-13; Jn. 5:28f).
Holy Scripture is not a scientific cosmogony, that is, a detailed account of the creation of the universe, nor a complete development of human history. The Holy Bible speaks mainly of the faith we must have in God and about our relationship with Him. We cannot enter into the details of the eternal will and plan of God. We know God and His plans only to the extent that they are revealed to us, and as they are realized in history. And God has revealed to us what is needed for our salvation. But we shall see everything face to face when they actually come to pass before us. Christians must know now that Christ will come as king and judge (Mt. 14:62). He will come at a time when we do not expect Him. This is why we must always be on guard, awake, and vigilant as sons and daughters of the light and of the day (Mt. 24:42; 25:13; Mk. 13:33-37; 1 Thess. 5:4-11; 2 Thess. 2:2; 3:11).
A Christian life is required of us, not curiosity about years and times "which the Father has placed under his own authority" (Acts 1:7). We do not live our lives as Christians out of fear that the coming of Christ is near, nor because we hope to gain rewards. We are Christians because we believe in the love of God, and we live a life in Christ out of love, being always ready to receive Him with great anticipation. We are challenged to live with the hope of the Parousia as did the early Christians who prayed: "Maranatha Come, Lord" (1 Cor. 16:22; Rev. 22:20; 1 Pet. 1:3-12). This is the way the early Christians lived their faith in the Church. But do we today have this faith and do we live with this hope? We never have enough; we always need more faith, more love, more prayer of hope: "Come, O Lord"
Source: At the End of Time: The Eschatological Expectations of the Church