Hello Poinsetta,
Just curious as to why you would think that the world is only 2000 years old? Jesus was crucified 2000 years ago and there is much human history prior to that.
From my understanding, mankind has been on the earth for approx. 6000 years.
Also, the way that it is stated in Genesis regarding the creation, the earth was already here without form and empty and completely covered with water. Therefore, the six days of creation doesn't include the creation of the earth itself, but everything on it, as well as the sun, moon and stars being created on the fourth day. In fact, the earth existed before everything else.
The conclusion then is that, we don't know how long the earth has been here. But we know that mankind and all that was created during the six days, has been here for 6000 years.