Jesus must come back twice to fulfill everything said about him in the Bible.

Jesus will come back at the very end of the Great Tribulation. In the middle of the Great Tribulation the antichrist will desecrate the Temple. From that point it will be 1,260 days until Jesus returns. So we'll know the exact day of Jesus's return at the end.

Yet we know that Jesus will also come like a thief. He'll come at a time when nobody expects and leave with all those who are believers at that time. He'll come when nobody sees him but at the end of the Great Tribulation everyone will see him coming on the clouds of heaven.