"And as he sat upon the mount of Olives, the disciples came unto him privately, saying, Tell us, when shall these things be? and what shall be the sign of thy coming, and of the end of the world? Matthew 24:3
[video=youtube;t-Oht7cVEHw]https://www.youtube.com/watch?feature=player_detailpage&v=t-Oht7cVEHw#t=2[/video]
"Immediately "after" the tribulation of "those days" shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken: And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory.And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other." Matthew 24:29-31
The expression "from one end of heaven to the other" denotes that they shall be gathered from all parts of the earth where they are scattered. The word "heaven" is used here to denote the "visible" heavens or the sky, meaning that through "the whole world" he would gather them. See Jeremiah 31:10, Zechariah 2:6, and Deuteronomy 4:32