Time is against you. Each day that passes brings you a day closer to death. For every day your character survives, check off a day on your personal calendar that is part of your character record. In fact, it takes up an entire page until itself.
Each day you survive, reduce all your skills by 1 point and increase your Determination by 1. If you survive long enough, you may even become slightly conditioned to the world after the disaster. It won’t save characters from death, but it might give them the edge they need to achieve their goals. Time also determines how many Threats the GM gets.