Why does time go forward and not backwards? This might seem like a simple question, but it's actually really complicated. Most of the laws of physics are symmetric with respect to time. That means that it doesn't matter whether time moves forward or backwards. If time ran in reverse, all the laws of physics would work the same.
That is, all the laws except one. The Second Law of Thermodynamics does imply a direction. The Second Law states that over time, everything moves from an ordered state to a disordered state. It's the only physical law that can't go backwards.