I believe evolutionists leave the assessment of the earth's age to geologists and astronomers, who have the training, knowledge, and tools to make the best estimate possible with current technology.
I don't mean to be a contrarian, but I'm going to.
I'm pretty sure biologists determine the age of the earth, not geologists and the other kind of ologists that you mentioned. Biologists use the discredited theory of evilution. I've never really understood exactly how they do that, I think it has something to do with either tree rings or the half life of the bacteria in Thomas Huxley's bedroom slippers. But I'm quite sure that the theory of evilution is behind it all. Then eveyone else just agrees with that, assuming it's correct since nobody else has any better ideas.
Those who would sacrifice an essential liberty for a temporary security will lose both, and deserve neither. -- Benjamin Franklin