先与后时间的方向在于先后之间的不同,这种不同不易确定。先和后的相互关系没有不同,因为它们正好是互为反面。这就是说,如果一任意的事件或日期e先于某事件或日期e*,则e*后于e——反之亦然。在形式属性上它们也没有什么不同,即都是非自反的、传递的和不对称的。也就是说,没有哪个e会先于或后于它自身;对于e、e*和e**来说,如果e先于(后于)e*,而 The difference between the first and the last time lies in the difference between the first and the second. This difference is not easy to determine. There is no difference between first and second, because they happen to be the opposite of each other. This means that if an event or date e precedes an event or date e * then e * is followed by e - and vice versa. They also have no difference in formal attributes, that is, they are nonreflexive, transmitted and asymmetrical. That is, no e precedes or follows itself; for e, e * and e **, if e precedes (after) e * and