Didn’t realise they could date back that far.
It is depending on if you are dating rocks or minerals.
There are only few places on Earth, where you can find rocks from the Hadean Eon: geological shields n Africa, Canada and Australia.
Hadean Eon (from 4.6 to 4.0 billion years ago) is the oldest of 3 divisions (eons) of the super-eon Precambrian (4.6 billion years ago to 541 million years ago. The other 2 eons being Archean and Proterozoic.
The oldest rock was discovered Acasta Gneiss, Slave craton, Canada, felsic rock dated to 4.031 ±0.003 billion years old.
On the other hand, crystal of mineral, like zircon are older.
The oldest zircon was discovered at Jack Hills in Western Australia, has been dated to 4.404 ±0.008 billion years old.
You cannot use carbon-14 isotopes in radiometric dating method, because they only have half-life of 5730 years, and only accurate dating objects of 55,000 years or less.
Hence, other radioactive isotopes must be used to dating anything older than 1 million year.
Potassium-40 (K-40), which is used in Potassium-Argon (K-Ar) radiometric dating, has half-life of 1.248 billion years. Therefore, it can date anything from 10,000 years to several billion of years.
Isotopes Uranium-235 and Uranium-238 (used in Uranium-Lead (U-Pb) radiometric) provide more accurate results than K-40. U-235 has a half-life of 710 million years, while U-238 has a half-life of 4.47 billion years.
All 3 isotopes can measure rocks or minerals of a billion years or more. I had mentioned these 3 isotopes because they are most commonly used in dating geological stratigraphy.
There are many more radioactive isotopes that can be used and a few have even longer half-life than U-238.
For examples, isotopes 147 and 148 of Samarium have respective half-life of 106 billion years and 10^17 years.
Radiometric datings, not only can date rocks and minerals on earth, but also moon rocks collected from the Apollo missions, and any meteorites that have crashed to Earth.
One famous meteorite crashed near the town of Murchison, Victoria, Australia, in 1969. The Murchison meteorite not only contained some organic compounds (eg amino acids), but also silicon carbide.
My point is that silicon carbide are rarely found natural on earth, but they are more abundant in space, like this Murchison meteorite, and it has been dated to over 7 billion years. This mean that Murchison meteorite is older than the Solar System, older than Earth!