You seem to be confused about the difference between "how God created the earth" and "if God created the earth." The Bible does not say how, only what the end result of that creation process became. The Bible also does not state when the earth was created, or how old it is.
The Bible doesn't say how old the earth is, and science has no way to date a fossil older than 5'000 years except through pure guess work.
The first creative day didn't begin until Genesis 1:3. The universe and the earth were created in verses 1 and 2 of that chapter. Also the Hebrew word for "day" can mean any marked period of time, such as "the day of harvest". It is similar to the English word "day" in that regard. Even in the context of Genesis chapters one and two the word "day" is used in several different ways. Moses himself also used the word "day" in a similar way as did Peter.
BOOK FOUR
(Psalms 90 – 106)
A prayer of Moses, the man of the [true] God.
(Psalm 90:4) 4 For a thousand years are in your eyes but as yesterday when it is past, And as a watch during the night.
(2 Peter 3:8) 8 However, let this one fact not be escaping YOUR notice, beloved ones, that one day is with Jehovah as a thousand years and a thousand years as one day.
Some fundamentalists claim that "day" in the first chapters of Genesis must be 24 hours because of what is stated at Exodus chapter 20:
(Exodus 20:11) 11 For in six days Jehovah made the heavens and the earth, the sea and everything that is in them, and he proceeded to rest on the seventh day. That is why Jehovah blessed the sabbath day and proceeded to make it sacred.
However the :heavens and the earth mentioned here are not the same as Genesis 1:1, but is grouped with "the sea and everything that is in them" and refers to events of days 2,3,5, and 6.
As for dating metholds, there isn't any reliable one for fossils that works past dates that can confirmed with tree rings, which is not a very exact science either.
The Uranium-Lead clock has a half life of 4.5 billion years. We do not have to know how much uranium was in the rock to start with because all we have to measure is the proportion of lead to uranium at the end of the period. However, the rock has to be free from lead at the beginning. This is usually not the case; there is some lead to start with. This gives the rock what is called a built-in age, something more than zero. Also, we assumed that the uranium was tightly sealed in the rock so that nothing could get in or out. Sometimes this may be true but not always. Over long periods of time, some of the lead or the uranium might seep out into groundwater. Or more uranium or lead might get in, especially if it is a sedimentary rock. For this reason, the uranium-lead clock works best on igneous rocks.
The one that has been most widely used is the potassium-argon clock. Potassium is a more common element than uranium—potassium chloride is sold in grocery stores as a substitute for common salt. It consists mostly of two isotopes with masses 39 and 41, but a third isotope, of mass 40, is weakly radioactive. One of the products of its decay is argon, an inert gas that makes up about 1 percent of the atmosphere. The potassium of mass 40 has a half-life of 1.4 billion years, which makes it suitable in measuring a range of ages from tens of millions up to billions of years.
Another radioactive clock for minerals has been developed more recently. It is based on the decay of rubidium into strontium. Rubidium decays incredibly slowly. Its half-life is 50 billion years.
"For example, when we understand that the Bible uses the term “day” to represent various periods of time, we see that the account of the six creative days in Genesis need not conflict with the scientific conclusion that the age of the earth is about four and a half billion years. According to the Bible, the earth existed for an unstated period before the creative days began. (See the box “The Creative Days—24 Hours Each?”) Even if science corrects itself and suggests a different age for our planet, the statements made in the Bible still hold true. Instead of contradicting the Bible, science in this and many other cases actually provides us with voluminous supplemental information about the physical world, both present and past."