"Joseph Smith, Jr.  unapologetically claimed that Christianity - with all it's elements - had been preached since Adam"  - Jona Barnes, Kay to the Keystone, pg. 25

"...and the first came and stood before my father, and gave unto him a book, and bade him that he should read... And it came to pass that when my father had read and seen many great and marvelous things... he testified that the things which he saw and heard, and also the things which he read in the book, manifested plainly of the coming of a Messiah, and also the redemption of the world."   -- 1 Nephi 1

"...for this intent have we written these things, that they may know that we knew of Christ, and we had a hope of his glory many hundred years before his coming; and not only we ourselves had a hope of his glory, but also all the holy prophets which were before us."  - Jacob 4:4

"And the Messiah cometh in the fulness of time, that he may redeem the children of men from the fall." - 2 Nephi 2:26

The Father COVENANTED with Adam that he would send His SON in the meridian of time...

Adam, Seth, Enoch, Noah, Abraham, Joseph...

All of the ancient prophets KNEW details of Christ's birth: His Name and Mission (Matt 1:21), His place of Birth (Matt 2:3-6), etc...

"For according to the words of the prophets, the Messiah cometh in six hundred years from the time that my father left Jerusalem; and according to the words of the prophets, and also the word of the angel of God, his name shall be Jesus Christ, the Son of God... For we labor diligently to write, to persuade our children, and also our brethren, to believe in Christ, and to be reconciled to God; for we know that it is by grace that we are saved, after all we can do. And, notwithstanding we believe in Christ, we keep the law of Moses, and look forward with steadfastness unto Christ, until the law shall be fulfilled.  For, for this end was the law given... And we talk of Christ, we rejoice in Christ, we preach of Christ, we prophesy of Christ, and we write according to our prophecies, that our children may know to what source they may look for a remission of their sins." - 2 Nephi 25

1 Corinthians 15:3-4

"Now I would remind you, brothers, of the gospel I preached to you, which you received, in which you stand, and by which you are being saved, if you hold fast to the word I preached to you—unless you believed in vain. For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures, that he was buried, that he was raised on the third day in accordance with the Scriptures..."

WHAT "Scriptures"?  

Nothing in the Old Testament...