How old is the world?

As of 2014, according to the U.S. Geological Survey, the best estimate of the age of the Earth is 4.54 billion years, based largely on the apparent age of meteorites that were presumably formed at the same time. The oldest dated earth rocks are 4.4 billion years old.

There is fairly close agreement between the measured ages of the oldest earth rocks, 4.4 billion years old, the oldest moon rocks, 4.4 to 4.5 billion years old, and the oldest meteorites, 4.54 billion years old, suggesting that all were formed at roughly the same time. Dating of these rocks derives from isotopic ratios of the final, stable products of several radioactive decay series.