How does the Bible explain the existence of fossils that are millions of years old?

Wouldn't a better question be "how does anything other than the Bible explain the existence of the 'Millions of fossils'?"

In order to become fossilized, animals must die in a watery environment and become buried in the mud and silt.

A global flood would bury millions of animals in mud and silt, including large animals like dinosaurs.

Now as to fossils that are millions of years old, do they say that they are old because they have found evidence that they are(with no contradicting evidence) or because they expect the world to be that old in the first place(to support their other theories) and format their calculations to fit?

You say in your question that we are yet to find a single human. This is not true. "Neanderthal man" (men/women) are very human, despite what is often portrayed in popular culture, and for the large part, are fossils. Not all fossils are stone, actually. Many of them still contain tissue, genetic information etc.

It is actually just an assumption (intentionally) that they are millions of years old. In reality, the evidence (continuous sedimentary rock layers spanning the entire earth, fossils of various species grouped in herding patterns yet apparently buried together, most fossils being disarticulated, and more) points toward the global flood described in Genesis, which in fact also mentions more than water (potential volcanic and tectonic activity is also inferred, because the fountains of the deep were broken up).

It is actually more of a stretch to think that the fossils appear because they are millions of years before us. The very existence of "living fossils" which continue to be discovered over and over, helps to lend to the idea that the species are either contemporaries with mankind, or that we have gotten mixed up somewhere in our thinking to imagine them going extinct millions of years ago.

As to whether the Bible explains "millions of years" for fossils: no. It does not indicate that the earth itself is yet that old, and the evidence we have before us actually fits that model (but this is not the place to go into the full details of that).

Also, the Bible is a book of science. Just to point out how much so; The original Hebrew scriptures contain not only prophetic codes, but also scientific information. (The Bible codes, much disputed, but very accurate).

The Bible is also littered with scientific information: pathways in the sea, the store houses of snow and hail, etc. To cover all, or even a few, would take more time than I have, but of course - the main point is, the Bible is a well rounded book covering all disciplines, because it is the Word of God, and He created all things, and all you need to do, is seek and you will find.

OK, real answer for a real question.

God's revealed truth transcends time and space and doesn't have anything to do with the pursuit of scientific knowledge. The account of the world's creation, the story of human creation, the details of our fall are told to drive a point about man's relationship with God.

Scriptures don't prove that dinosaurs exist. But, God does say in His answer to Job that Job wouldn't want to tangle with any sea monsters. There were creatures (nephilim) who were not quite human in Genesis (Gen 6:4). So you can infer what you like, I personally don't understand either of these passages.

God, exists outside of time so we can't comprehend His mysterious ways.

The only scientific truth in the Bible is that it rains on the just and the unjust. That is, the only scientific truth in the Bible are tautologies.

The existence of fossils is explained by the world-wide flood in Genesis. As for the existence of fossils that are "millions of years old", the dating methods implied are in question by the scientific Christian community.

You can find more information about why Christians believe this at creationism sites like http://www.answersingenesis.org/ or http://icr.org.

The Bible does not explain anything about fossils. Fossils were unknown when the Bible was written. Fossils only become an issue if you interpret the Bible to believe that the Earth is younger than the fossil record shows. This is far from the only interpretation of the Bible. The question should be: How do people who believe that the Earth is only 6000 years old explain the existence of fossils. That is far too complicated a question to answer here.

2nd Peter 3:8 KJV reads:

But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day.

This is Peter writing to address the questions saying "Where is the Lord? He said he would return soon!"

Matthew 13:13 KJV reads:

Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand.

Genesis 1:5 KJV reads (emphasis mine):

And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.

Every man understands what a day is. It's possible God revealed this using these words so that even the unlearned (us) could understand the basic ideas of his word throughout the ages.

God speaks in parables and metaphors (thanks, Anthony!) because as mortal beings, we are stuck in our own little frames of reference. I don't know exactly what it takes to build a planet from nothing, but from what I've learned in my life it would take a lot of matter, a lot of pressure, and a lot of time.

It could very well have taken billions of years, we don't know. As they say, God works in mysterious ways.