The 7 thousand years mentioned in the hadiths as the lifespan of the world refers to the beginning of a calendar
Excerpt from Mr. Adnan Oktar's Live Interview on A9 TV dated December 12th, 2011
ADNAN OKTAR: Well, this friend of ours has been obsessed with this matter; we've been explaining it time after time and they still fail to understand. They've been saying ; "Master you are talking about many million years old fossils, there is a link in your website which shows a fifteen thousand years old fossil." My brother that seven thousand years does not mean that the world has been created only seven thousand years ago. That is a calendar of seven thousand years. Now we are in 2011, are we not?
ADNAN OKTAR: Has the world been created 2011 years ago? No, it has not. It is 1433 according to the Hegira calendar. So has the world been created 1433 years ago? No, it has not. This seven thousand years is a calendar. The creation of the Prophet Adam (pbuh) dates back to approximately 200 thousand years or so, in my opinion. I mean it should be about 150 thousand to 200 thousand years ago, or let us say it was 100 thousand years ago. Insha'Allah. I mean it is about those dates. Insha'Allah. That is because they are unable to make such a precise and definitive determination. But it is about that much..