Where do we even start? Time is important to Foundation in all of its modes: past, present, and future. The future is obvious: Seldon set up the science club not only to fight against an apocalyptic future but also to bring about the Second Empire. Hey, no pressure guys, just the future of the galaxy and a bag of chips. But don't forget the past: sure, you need to learn from it, but it can be dangerous if you start thinking it's the end-all, be-all of decision-making. Hey, it worked in the past; it should work now, right? Wrong. The heroes in Foundation are the men (sorry again, ladies) who can learn from the past, recognize what needs to be done in the present, and work toward the future. Easy-peasy.
Seldon's Plan is not so much about predicting the future as assuming that the future will be a repetition of the past.
Hardin and Mallow are the heroes of the Foundation, because they understand the relationship between the past and the future.