It does not give dates of millions of years and when corrected properly fits well with the biblical flood.
There are various other radiometric dating methods used today to give ages of millions or billions of years for rocks.
To derive ages from such measurements, unprovable assumptions have to be made such as: There is plenty of evidence that the radioisotope dating systems are not the infallible techniques many think, and that they are not measuring millions of years. For example, deeper rocks often tend to give older “ages.” Creationists agree that the deeper rocks are generally older, but not by millions of years.
Geologist John Woodmorappe, in his devastating critique of radioactive dating, points out that there are other large-scale trends in the rocks that have nothing to do with radioactive decay.
These techniques are applied to igneous rocks, and are normally seen as giving the time since solidification.
The flood buried a huge amount of carbon, which became coal, oil, etc., lowering the total C ratio in plants/animals/the atmosphere before the flood had to be lower than what it is now.It cannot be used to date volcanic rocks, for example.The rate of decay of N in 5,730 years (plus or minus 40 years).So, we have a “clock” which starts ticking the moment something dies.Obviously, this works only for things which were once living.