I guess it depends what you mean by "planet".
Up until roughly 3.5 to 4 billion years ago (the "Late Heavy Bombardment"), the "thing" that became our planet was still accumulating heavy chunks of stuff, so that you could say that our present mass is around 3.5 to 4 billion years aold.
The oldest material we have found on Earth shows that parts of this material is up to 4.5 billion years aold, so that the material assembled (on the "thing" which became Earth) around that time.
This age appears to match the age of the Solar system since the Sun became a full-fledged star (when the fusion of hydrogen began in its core) and also the age of the oldest "stuff" that is being collected from interplanetary space and also from comets and asteroids.
Because of that, most people say that Earth is around 4.5 billion years old.
If you had been a visitor to the baby-solar-system around that time, you would have seen a lot of junk still moving around all over the place. But you would have seen one chunk, much bigger than the others, and you would have said: that is the chunk that is becoming the main planet at this distance from the Sun. That chunk was already the "thing" that became Earth.
Up until roughly 3.5 to 4 billion years ago (the "Late Heavy Bombardment"), the "thing" that became our planet was still accumulating heavy chunks of stuff, so that you could say that our present mass is around 3.5 to 4 billion years aold.
The oldest material we have found on Earth shows that parts of this material is up to 4.5 billion years aold, so that the material assembled (on the "thing" which became Earth) around that time.
This age appears to match the age of the Solar system since the Sun became a full-fledged star (when the fusion of hydrogen began in its core) and also the age of the oldest "stuff" that is being collected from interplanetary space and also from comets and asteroids.
Because of that, most people say that Earth is around 4.5 billion years old.
If you had been a visitor to the baby-solar-system around that time, you would have seen a lot of junk still moving around all over the place. But you would have seen one chunk, much bigger than the others, and you would have said: that is the chunk that is becoming the main planet at this distance from the Sun. That chunk was already the "thing" that became Earth.
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Earth ; ~4.5 Billion years .
Algae and bacteria ; ~2 Billion years .
Land plants ; ~430 Million years .
Reptiles ; ~300 Million years .
Modern mammals ; ~75 Million years .
First apes ; 3~5 Million years .
Ape-like men ; ~10 Million years .
Homosapien ; ~250,000 Years .
Algae and bacteria ; ~2 Billion years .
Land plants ; ~430 Million years .
Reptiles ; ~300 Million years .
Modern mammals ; ~75 Million years .
First apes ; 3~5 Million years .
Ape-like men ; ~10 Million years .
Homosapien ; ~250,000 Years .
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very old in human terms, 5 billion years but very young in galactic terms, only have way through its life.
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4600000000.
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Around 4.5 billion years old