by the time后面加什么时态的

You count such a watch by the time he starts his class.

你总是掐着他开始上课的时间。

Most of the workers had already rung in by the time I arrived.

我到的`时候，大多数工人都已签到了。

By the time she left college, she had been an excellent student.

到她大学毕业的时候，她已经是一个优秀的学生了。