Comment on Evolution vs Creation Debate by Jacob.
these bones are dated using what is called carbon dating, carbon dating reads the amount of a certain radioactive carbon isotope, this radioactive isotope has a very specific half life and all living things are made up of a certain percentage of this isotope (.0283341%).
by measuring the percentage of this isotope in the carbon remains we can see how much less carbon there is than what there should be. when we know that we can then calculate (to within 150 years) how old the fossil is.
so in answer to your question the age we give dinosaur bones is accurate to within 150 years, just a drop in the ocean compared to the 360,000 years since the supposed end of the dinosaurs.