Does the passage of time depend on speed only or on the direction as well? As far as I understand, the passage of time is different for a person approaching me and different for a person leaving me. So isn't velocity the cause of time? If not, why not? I am not an expert in Physics, I completed my college or high-school if you call it that way and am trying to pursue a career in Aviation Science, along with Physics as a passion. If possible, please do explain in layman's term, as I don't have enough understanding of advanced physics. PS - I don't believe in the concept of time. It's rather an illusion for me. As time is more of a philosophical study too, hence I wouldn't want to argue on this. Please just let me know whether space-time, aka, time is dependent on speed or velocity? If not on velocity, please explain why. A bit of maths is okay, I can understand them.