The relativity of time is the fact that two events that may occur at the same moment, are actually not the same moment. It is a complex thought that may be confusing, but examples are helpful. In New York, someone wants to throw a baseball as far as they can. Let's say someone in Paris has the same exact idea, and they want to do it at the exact same time. The relativity of simultaneity is that when the balls are thrown, they will not be thrown at the exact same moment. Although they can say it was at the same time, form a distant observer (maybe up in a plane between the two countries), it will not be at the same moment. What is not relativity to simultaneity is appearance simultaneity. Norton uses an example that involves watching a star explode in space. Although we may think it just happened in the present, it may have happened 10 million years ago. Norton explains that you cannot clarify the relativity until the appearance factor is solved, because there is relativity to it. In special relativity, its extremely complicated to wonder if time is even relevant at all. If lightning strikes (like in Nortons example) from miles away, and the thunder comes seconds after, there clearly is a time factor. The movement of time plays a major role in relativity so I will say time is extremely relevant. Relativity of simultaneity is a very deep concept to ponder.