This is a "Fallacy of Irrelevance": When you introduce issues which have no logical bearing on the subject under discussion, you are using irrelevant arguments.
Muslims argue that the Koran is the Word of God because it contains some historically or scientifically accurate statements. This argument is irrelevant. Just because a book is correct on some historical or scientific point does not mean it is inspired. You cannot take the attributes of a part and apply it to the whole. A book can be a mixture of true and false statements. Thus it is a logical fallacy to argue that the entire Koran is true if it makes one true statement.
When a Muslim argues that history or science "proves" the Koran, this actually means that he is acknowledging that history and science can likewise refute the Koran. If the Koran contains just one historical error or one scientific error, then the Koran is not the Word of God. Verification and falsification go hand in hand.
Sadly, the koran also states that the sun sets into a "muddy stream" or some such nonsense.
You have stretched what the koran was saying to make it mean something that it never said or intended!
Furthermore, that is a plagiarized statement from the Bible.
If the koran is accurate because of that statement, then the Bible is even more accurate, because it said it first, and yet you reject the Bible!
This also makes it a "Fallacy of False Assumptions": In logic as well as in law, "historical precedent" means that the burden of proof rests on those who set forth new theories and not on those whose ideas have already been verified. The old tests the new. The already established authority judges any new claims to authority.
Since Islam came along many centuries after Christianity, Islam has the burden of proof and not Christianity. The Bible tests and judges the Koran. When the Bible and The Koran contradict each other, the Bible must logically be given first place as the older authority. The Koran is in error until it proves itself.
Muslims violate the principle of historical precedent by asserting that Islam does not have the burden of proof and that the Koran judges the Bible.
EDIT:
You ask who says this was already in the Bible? LIKE DUH! Now you've gone over the line in stupidity and insanity! The Bible clearly says that "A day, to the Lord, as as a thousand years, and a thousand years is as a day."