Radiometric dating christian
Even in the case of very long half-lives, modern scientific instruments are now accurate enough to give very fine readings.
We usually hear of Carbon 14 dating, which is very important in archaeology.
These elements have much longer half-lives than Carbon, and in some cases can be cross-referenced if more than one of these elements is present in a volcanic tuft.
There are other methods for dating fossils, such as thermoluminescence.
Tree ring data (dendrochronology) can be used to even out this inconsistency, however the oldest trees used for calibration are in the order to about 6,000 years old, so any further back than that and you can't correct your dates (although there are reportedly some preserved huon pines in Tasmania that could take this right back to 30,000 years or so, if anyone wants to spend half their life time counting tree rings).
Even if dates are corrected with tree ring data they are still not considered calendar years, but rather radiocarbon years.
So a 40,000 year C-14 date and a 60,000 year thermoluminescence date could easily come from the same strata, right next to each other, and possibly reflect a date of anything between 30,000 and 70,000 calendar years depending on the standard deviations of your dates.
Dates were estimated according to the supposed rate of deposition of rocks, and figures of several hundred million years were bandied out; usually arrived at through inspired guesswork rather than anything else.The radioactive isotope Carbon 14 has a half-life of 5,730 years.This has made it useful for measuring prehistory and events occurring within the past 35 to 50 thousand years.(The item being tested must be organic based, and must be dead - tests on live mollusks showed an age of 2000 years).If a fossil is completely replaced (permineralized), then it would be useless in a similar test - because it no longer is organic.