The Earth is an estimated 4.54 billion years old; there's an old rock in Australia that's 4.4 billion years old!
The rock was discovered nearly 30 years ago, and is known as the oldest known rock on Earth. Investigation of the ancient crystals in the rock reveal that the new planet already had oceans and may have had life on it back then. It's possible that in its earlier history, Earth saw oceans appear and disappear, along with early life forms that evolved and were wiped out in those turbulent times. If you're a classic rock fan you should read more about this amazing specimen. There's also another rock in the Hudson Bay in Quebec that might be even older!
The planetary age is based on calculations of the radiometric age of meteorites. It has also been found to be consistent with the ages of the oldest known rock samples both on Earth and from the Moon. On the other hand, the Milky Way Galaxy has an estimated age of 11 to 13 billion years and the age of the universe is dated somewhere within the range of 10 to 15 billion years. These approximations are based upon the evolution of globular cluster stars and the recession of distant galaxies. Read more about the age of the Earth.