In the Gospel of Luke, our Lord Jesus Christ tells us beforehand everything is about to happen before that frightening day to prepare us so that we may not be led into error.
`Teacher,` they asked, `when will these things happen? And what will be the sign that they are about to take place?`
He replied: `Watch out that you are not deceived. For many will come in my name, claiming, ‘I am he,’ and, ‘The time is near.’ Do not follow them. When you hear of wars and uprisings, do not be frightened. These things must happen first, but the end will not come right away.`
Then he said to them: `Nation will rise against nation, and kingdom against kingdom. There will be great earthquakes, famines and pestilences in various places, and fearful events and great signs from heaven.
But before all this, they will seize you and persecute you. They will hand you over to synagogues and put you in prison, and you will be brought before kings and governors, and all on account of my name. And so you will bear testimony to me. But make up your mind not to worry beforehand how you will defend yourselves. For I will give you words and wisdom that none of your adversaries will be able to resist or contradict. You will be betrayed even by parents, brothers and sisters, relatives and friends, and they will put some of you to death. Everyone will hate you because of me. But not a hair of your head will perish. Stand firm, and you will win life.
When you see Jerusalem being surrounded by armies, you will know that its desolation is near. Then let those who are in Judea flee to the mountains, let those in the city get out, and let those in the country not enter the city. For this is the time of punishment in fulfillment of all that has been written. How dreadful it will be in those days for pregnant women and nursing mothers! There will be great distress in the land and wrath against this people. They will fall by the sword and will be taken as prisoners to all the nations. Jerusalem will be trampled on by the Gentiles until the times of the Gentiles are fulfilled.
There will be signs in the sun, moon and stars. On the earth, nations will be in anguish and perplexity at the roaring and tossing of the sea. People will faint from terror, apprehensive of what is coming on the world, for the heavenly bodies will be shaken. At that time they will see the Son of Man coming in a cloud with power and great glory. When these things begin to take place, stand up and lift up your heads, because your redemption is drawing near.
He told them this parable: Look at the fig tree and all the trees. When they sprout leaves, you can see for yourselves and know that summer is near. Even so, when you see these things happening, you know that the kingdom of God is near.
Truly I tell you, this generation will certainly not pass away until all these things have happened. Heaven and earth will pass away, but my words will never pass away.
Be careful, or your hearts will be weighed down with carousing, drunkenness and the anxieties of life, and that day will close on you suddenly like a trap. For it will come on all those who live on the face of the whole earth. Be always on the watch, and pray that you may be able to escape all that is about to happen, and that you may be able to stand before the Son of Man.”
`Heaven and earth will pass away but My words shall not pass away.` My words will remains, they will become reality, they will take place in the life of men as it is said here. `Many will come in My name claiming `I am He`. As we believe and expect that antichrist will say: `I am Christ, I am God. Come to me, I will give you everything. It is enough to believe in me and receive the seal of obedience towards me.` The Jews thought this antichrist was Messiah who was to come to reign over an Judaic kingdom. They will build their temple, they will make their state and all the rest. `Do not go after them. When you hear about wars and commotions do not get alarmed` There will be wars and many commotions but don not be afraid, do not lose your courage, do not lessen your faith in Me.
Be steady in faith because there will be such terrible signs that because of the fear and expectation of what is to come the men will lose their faith, their courage, they will be constrained and because of such a big fear they will be almost dying. `And then they shall see the Son of Man coming on the clouds in great power and glory.`
Therefore beware to yourself, so that you may not be found on this terrible frightening day in a sinful state, in drunkenness, enslaved by the multitude of worries of this life. Prepare yourself by confessing, cleansed and ready for such a great day when God will judge the world. This will come like a trap: it will be so unexpectedly that the people will be taken by surprise. Be vigilant and do not sleep! Be vigilant in your prayers, in your cogitations, in your current affairs, in your family life and everywhere permanently so that you won`t fall into sin and be worthy to stand on the right side of Christ, the Great Judge.
Saint Paul, the Apostle describes the glorious coming of Christ, our Lord. He says in one of his epistles that `the Lord himself will come down from heaven, with a loud command, with the voice of the archangel and with the trumpet call of God, and the dead in Christ will rise first. After that, we who are still alive and are left will be caught up together with them in the clouds to meet the Lord in the air. And so we will be with the Lord forever.`
Meaning that the voice of the Son of God will call first the reposed ones to come back to life from the dead. And when they are resurrected we will see them taken on clouds. The revived people will leave like the aerostats to go and stand on the right side of Christ.
Those who will be alive then will be taken on clouds and brought to greet the Lord in the skies. Those who will be taken on clouds to greet the Lord will be the saved ones, the righteous who will stand on His right.
 Luke 21, 7-36.
 1 Thessalonians 4, 15-17.
Excerpt from the book The Art of Salvation published by Evanghelismos.