When the resurrected Christ returned to the right hand of God, angels announced to the apostles, "...This same Jesus, who was taken up from you into heaven, will so come in like manner as you saw Him go into heaven" (Acts 1:11).
Many people speculate concerning when Jesus will return. Jesus plainly said that no one but the Father knows when that day and hour will be (Matt. 24:36). But He did say that it would be on a day and hour in which no one would be expecting Him, even though He has told us that He is coming (Matt. 24:50).
Rather than being concerned about when Jesus will return, we should be concerned about why He is returning. Jesus said that He WILL return to judge every person (John 12:48; Matt. 25:31-32; Rom. 2:16). Therefore, He tells us to, "BE READY: for in such an hour as you think not the Son of man cometh" (Matt 24:44; cf. Matt. 24:36, 42, 50; 25:13).
To be ready for His return, you must Believe He is Christ, The Lord (John 8:24; Acts 2:36), Repent, i.e., turn your heart from sin to follow Him (Luke 13:3, 5; Acts 26:20), Confess Him (Matt. 10:30; Acts 8:37), Be Baptized for the remission of your sins (Mark 16:16; Acts 2:38), and continue to Abide in His word (John 8:31-32; Acts 2:42).
Jesus said, "these (the unprepared) shall go away into everlasting punishment: but the righteous into life eternal" (Matt. 25:56). He's coming! Be ready!