The really important part of Jesus' statement in Matthew 25:13 isn't even the fact that He said no one will know ehen He's going to return. What's really important is that we're to "Watch!"
And even though the world may laugh at the idea of Jesus returing, so what? They're laughing doesn't alter what God has in store. Jesus is coming back because He Himself said so!
John 14:3
(3) And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also.
One of the more intriguing statements in the New Testament is the following from the book of Hebrews:
Hebrews 9:28
(28) So Christ was once offered to bear the sins of many; and unto them that look for him shall he appear the second time without sin unto salvation.
We're supposed to be looking for His coming as His return is imminent. Just because He hasn't returned yet doesn't mean He isn't going to. He's coming; count on it.
Here are just a few of the New Testament warnings about the need to watch:
Matthew 24:42-44
(42) Watch therefore: for ye know not what hour your Lord doth come.
(43) But know this, that if the goodman of the house had known in what watch the thief would come, he would have watched, and would not have suffered his house to be broken up.
(44) Therefore be ye also ready: for in such an hour as ye think not the Son of man cometh.
Mark 13:33-37
(33) Take ye heed, watch and pray: for ye know not when the time is.
(34) For the Son of man is as a man taking a far journey, who left his house, and gave authority to his servants, and to every man his work, and commanded the porter to watch.
(35) Watch ye therefore: for ye know not when the master of the house cometh, at even, or at midnight, or at the cockcrowing, or in the morning:
(36) Lest coming suddenly he find you sleeping.
(37) And what I say unto you I say unto all, Watch.
Luke 21:36
(36) Watch ye therefore, and pray always, that ye may be accounted worthy to escape all these things that shall come to pass, and to stand before the Son of man.
1 Corinthians 16:13
(13) Watch ye, stand fast in the faith, quit you like men, be strong.
1 Thessalonians 5:6
(6) Therefore let us not sleep, as do others; but let us watch and be sober.
1 Peter 4:7
(7) But the end of all things is at hand: be ye therefore sober, and watch unto prayer.
1 Peter 5:8 Be sober, be vigilant; because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour:
Revelation 16:15
(15) Behold, I come as a thief. Blessed is he that watcheth, and keepeth his garments, lest he walk naked, and they see his shame.
Don't get discouraged by a scoffing world or the ridiculous claims of self-styled prophets. Weigh everything against the Word of God as He will never let you down.