There is information about the backstory/setup for Rage on the official site, as well as the first 50 pages of the tie-in book that was released a month ago. The problem is that some of the details of events leading up to the asteroid impact are not the same between them.

From the website, the public is not told that the Apophis asteroid will likely strike the planet, even after many governments become aware in 2024. It is not until August 2029 that "News reaches the general population as smaller meteorites impact the Earth ahead of Apophis. The Ark project is initiated." Then it says Apophis itself strikes Earth in December 2029.

Then we have the novel. The main character starts off knowing nothing about the impending arrival of Apophis. References are consistent with the idea that its fall, but everthing seems to be normal in the world. But when he is finally told what is going on, it's just over 2 days prior to the expected impact. Later, through the eyes of a different character getting ready to enter an ark right before impact, we get some references to general population uprisings and anger.

But the two versions seem inconsistent about how much the public knew and when.