The Second Coming of Christ is explicitly referred to 1,845 times in the Bible. When Jesus descended into heaven after his 33 years on earth, the angels stated that He would come back.

Acts 1:9-11
And after He (Jesus) had said these things, He was lifted up while they were looking on, and a cloud received Him out of their sight. And as they were gazing intently into the sky while He was departing, behold, two men in white clothing (angels) stood beside them; and they also said, "Men of Galilee, why do you stand looking up into the sky? This Jesus, who has been taken up from you into heaven, will come in just the same way as you have watched Him go into heaven."

Zechariah 14:4 also states that Jesus will return to earth at the Mount of Olives.

Zechariah 14:4
And in that day His feet will stand on the Mount of Olives, which is in front of Jerusalem in the east; and the Mount of Olives will be split in its middle from east to west by a very large valley, so that half of the mountain will move toward the north and the other half toward the south.

Jesus is coming back for several reasons but the two most important are (1) to conquer the Antichrist and his armies (Rev 19:19-21) and (2) to gather together and restore the nation of Israel. The fact that Jesus returns to defeat the Antichrist means that His second coming is at the end of the Tribulation, at the war of Armegaddon.

Read more in The Complete Book of Bible Prophecy