 According to standard presentations of special relativity, there is no fact of the matter as to whether two spatially separated events happen at the same time. This principle, which is known as the relativity of simultaneity, creates serious difficulty for the A-theory in general and for presentism in particular. After all, it follows from the relativity of simultaneity that there is no fact of the matter as to what is present, and according to any A-theory there is an important distinction between what is present and what is merely past or future. According to presentism, that distinction is one of existence—only what is present exists.