system
Given the following post, respond as if you're commenting on Reddit:
human
How is a man made item dated to 3000 or 40,000 years ago? I understand carbon dating to a degree but that would just tell us the age of the material, not when it was fashioned into say, a crystal dagger, would it?
gpt
Carbon dating tells you when a living thing died. It stopped taking in new carbon and all the existing carbon starts to decay if its carbon 14. The ratio of total carbon to carbon 14 is what tells you how hold it is. Less carbon 14, the older it is because carbon 14 has decayed away.

For a rock, they may use uranium isotope ratios in a similar way. 

For the dagger that's in the news, they may have found stuff made of previously living material around the dagger and carbon-dated those things, then used their age for the dagger.