In an April 1843 general conference speech, Joseph Smith predicted that Jesus Christ would not return before he would reach the age of 85. He said, “Were I going to prophesy, I would say the end [of the world] would not come in 1844, 5, or 6, or in forty years. There are those of the rising generation who shall not taste death till Christ comes… I prophesy in the name of the Lord God, and let it be written-the Son of Man will not come in the clouds of heaven till I am eighty-five years old” (History of the Church 5:336).
Mormon Apostle Bruce R. McConkie noted that the “rising generation” spoken of by Smith referred to the children born on April 6, 1843. He explained that these would be the first members of the rising generation and that “all children born, however many years later, to the same parents would still be members of that same rising generation.”
McConkie believed that “it is not unreasonable to suppose that many young men had babies at the time of this prophecy and also had other children as much as 50 or 75 years later, assuming for instance that they were married again to younger women. This very probable assumption would bring the date up to, say, the 2nd decade in the 20th century — and the children so born would be members of that same rising generation of which the Prophet spoke. Now if these children lived to the normal age of men generally they would be alive well past the year 2000 A.D.” (Mormon Doctrine pp. 692-693).
The year 2000 is very important in Mormon theology. In his book The Promised Messiah (p.606), McConkie wrote, “We know categorically that from the fall of Adam to the Second Coming of Christ is a period of some six thousand years, and that the millennial era will then continue for another thousand years.” This reasoning led McConkie to believe that the second coming could be very soon since the Doctrine and Covenants predicts that Christ will return “in the beginning of the seventh thousand years.” D&C 77:12 reads, “In the beginning of the seventh thousand years will the Lord God sanctify the earth, and complete the salvation of man, and judge all things, and shall redeem all things, except that which he hath not put into his power, when he shall have sealed all things, unto the end of all things; and the sounding of the trumpets of the seven angels are the preparing and finishing of his work, in the beginning of the seventh thousand years–the preparing of the way before the time of his coming.”
Joseph Smith was born in December of 1805 and didn’t come close to reaching 85. He died at the age of 38 in a gun battle while incarcerated in the jail at Carthage, Illinois.