意思不同而已

类似于中文 他已经坐了十年牢
和 他坐了十年牢 的区别

对啊，一般过去式和过去完成时不太好领悟

恕我直言：过多纠结于这些会浪费很多时间，大大拉低了学习效率。多听、多读地道资料，
见多了就可以悟出来。

回复 瓜族长胡瓜 :I HAVE FINISHED reading the 44-chapter tome A Global History from Prehistory to the 21st Century. Phew, what a relief! It took me nearly two long years, on and off, to make it. As a matter of fact, I started digging into it only this past January when my two-month break began. Of course, I HAD COVERED about four hundred out of the 750 pages before then.
现在完成时以目前为着眼点，而过去完成时以”过去的过去“为着眼点。
I hope this helps.

这个我通常翻译为已经和在什么什么之后