had done是什么时态怎么翻译

用法：

1、表示某一动作在过去某一时刻之前已完成。例如:

He had gone to bed by 10:00 last night.

昨夜十点钟之前他已上床去睡了。

2、与一般过去时搭配，表达某一动作在过去的动作发生时已完成。例如：

The train had started when I got to the station.

当我到达车站时火车已开走了。