What would you do?

I watched this movie last night. This guy time traveled into the near future. The world was destroyed and no one was left alive. He had no idea what happened. From searching around all he could figure out is that when he goes back to his time the world will end in 8 day's. What would you do if that was you? You come back knowing that in 8 day's the world is going to end and you have no idea how or why?