by the time. 的用法有哪些？

1、到...为止。一般要求主句用过去完成时。

He had left by the time we reached home.

当我们到家的时候他已经走了。

2、…当……的时候。如果只是说过去某个时候的状况，用过去时，而不用完成时。

By the time we arrived the meeting was over.

我们到达时，会议已结束了。