May and might are both ways of expressing possibility. Is there a difference between the way in which they should be used?
May和might这两个词汇都是可能性的不同表达。它们使用方法是否有不同呢？

Some people insist that you should use may (present tense) when talking about a current situation and might (past tense) when talking about an event that happened in the past. For example:
有人认为在谈论当前的情形时（现在时态）应该使用may，在谈论过去发生的事件时（过去时态）应使用might：

I may go home early if I’m tired. (present tense)
如果我觉的累了，我会早点回家。（现在时态）

He might have visited Italy before settling in Nuremberg. (past tense)
在他定居纽伦堡之前他可能去过意大利。（过去时态）

实际上，现在对这两个词的时态区分也已经很少了，一般情况下这两个词语可以互相替换。比如上面两个例句还可以这样写：

I might go home early if I’m tired.
如果我觉的累了，我会早点回家。

He may have visited Italy before settling in Nuremberg.
在他定居纽伦堡之前他可能去过意大利。

may和might有一些固定的区别:如果事情的真相在当时并不知晓，这种情况用may和might都是可以的：

By the time you read this, he may have made his decision.
到你读到它的时候，他可能已经做了决定。

I think that comment might have offended some people.
我认为这条评论可能会触犯一些人。

如果一些事在说话时已确定没有发生，这种情况最好用might：

The draw against Italy might have been a turning point, but it didn't turn out like that.
与意大利打成平局可能成为一个转折点，结果却并不是这样。