Jesus told his disciples what will happen at the time of his return.

Matthew 24:29-31

29 “Immediately after many people have suffered during those days, the universe will become dark. The sun will become dark. The moon will not shine. The stars will fall from the sky. And the powerful objects in the sky will be shaken. (OR, And the spiritual beings in space will be deposed.) 30 After that, something will be seen {people will observe something} in the sky that indicates that I, the one who came from heaven, am returning to the earth. Then unbelieving people from all ethnic groups of the earth will mourn because they will be afraid of God punishing them. They will see me, the one who came from heaven, coming on the clouds with power and great glory as I return to the earth. 31 I will send my angels to the earth from everywhere in the heavens. They will be blowing trumpets loudly. Then from throughout the whole earth [DOU] they will gather the people whom I have chosen.”