I get these kind of baiting questions all the time on another site on which I've answered questions for over 15 years. If you want to argue this point fine, go somewhere else, but if you want an honest answer I'll try to give you one.
First the most common fossil dating technique is relative dating. This comes from the fact that sediments are laid down in water or on the surface of the earth in layers so the first is the oldest and next is younger. Fossils are encased in the sediment when it was deposited and preserved.
So, the fossil can be determined to be of the same age of the sediment in which it is found or a bit older if it was eroded and deposited from older sediments.. The one exception that I know of is creatures that dig or bore into sediments, like crabs or trilobites. They could burrow into an underlying layer and become fossilized there, but in nearly all cases this would be accounted for in the "age range" assigned to the fossils of the creatures.
So if the Widget fossil is found in sediments in layers of rock below the Do-hicky fossil in the layers above it, then the Widget fossil is older and it can be assumed that it lived before the Do-hicky. If they are round mixed together, then it is assumed that the period of time they existed overlapped with one another. So this allows geologists and paleontologists to give rocks relative dates based on fossils and visa versa.
Rocks are classified as having been deposited in certain geologic periods based on events we know occurred on a global basis or on a more localized scale. The Cretaceous boundary marker bed, is based on the layer of ash that resulted on a world wide basis due to the asteroid impact that they think resulted in the mass extinction event that did in the dinosaurs. That layer only an inch or inches thick is found world wide in the rock record and contains Irridium at levels not found on the earth naturally.
So it serves as a instant in time around the world and can be used to correlate ages of rock around the globe. We know which rocks anywhere around the world were deposited before and after the event. Another way we can split the geologic time line into intervals or periods are based on fossil evidence of certain organisms. The Jurassic period the time of the Dinosaurs is an example. Cambrian and Ordivician and Silurian saw an increase in certain other organisms.
So discrete lines were drawn and refined later as we got a better understanding and found more fossils delineating the periods in which they lived more clearly.
So, it should be clear now that if you had a fossil shell in a rock in Virginia and found the same shell in a rock in Russia, that the shell found in both places was living during roughly the same time, not the same year, but within the geologic range of its existence. It could be millions of years. Just for example as if your bones are one day are found in the cemetery bone collection found in a sandstone a few million years from now by aliens exploring the earth.
They would not know that you died in , but only that you existed and lived during the several million years that homo sapiens inhabited the earth. They might classify that interval as the Bipedal Primate Period, and you lived in the Era of Petroleum, do distinguish you from other fossil remains that came from earlier civilizations of Bipedal Primates. Earth events also are used.
In the Triassic period there was an excess of Iron and lots of oxygen so sediments are found world wide from this period and they are called Triassic Red Beds due to their bright red rusty appearance.
In addition, Tectonic events were occurring such as continental breakups that resulted in a lot of tensional faulting and basin creation, and the red beds were deposited in these basins.
If these same fossils are found elsewhere in different types of rocks we know too that that rock was deposited in the same general range of time. One of the favorite ploys by Creationists is to say well how do you know the rocks haven't been turned upside down.
Well we do this pretty easily because bed forms form in sand and silts allowing us to tell if the rock has been folded or turned over. We can look at grain size, larger grains usually settle first, followed by smaller and then finer grains so we look at the particle size distribution. Yes there are exceptions to this but we know in what environments of deposition they occur and can distinguish the exception from the rule. Now once we have established a relative age we can try to fine tune the age of the fossil itself by radiometric methods that are considered Absolute Age methods meaning they can give us a rough age in years before present.
Carbon dating is based on the changes in the isotope ratios of stable forms of carbon and the unstable forms radioactive forms that decay into daughter isotopes of a known half life. A half life is the time it takes half the isotope to decay into the daughter isotope by shedding electrons.
This is what radioactive decay is. Sure it is not a precise day, week and month kid of dating method and usually results in a range that can vary quite a bit depending on the type and age of the fossil, but its better than trying to date something by counting the characters in the Bible and trying to come up with the time of creation of the Earth.
Of course that did not include the time the dinosaurs existed, since I don't recall any biblical reference to them on Noah's Ark.