by the time有两个含义和用法，首先要知道by所表示的时间是含the time在内的。
一)到...为止
by the time+过去时间，主句过去完成。by the time+将来时间，主句将来完成时。
1.如果从句中的谓语动词是一般过去时，那么主句中的谓语动词通常用过去完成时，表示“截到从句动作发生时，主句动作已经完成，即过去的过去”：
主句用had done+by the time+从句用一般过去时时态
By the time I was Vice Chancellor, Senate had become a much larger and a much more democratic body.
到了我当校长的时候，大学评议会的人员规模已显著扩大，也变得更加民主了。
The storms had abated by the time they rounded Cape Horn.
他们绕过合恩角时，暴风雨已经减弱。
He had left by the time we reached home.
当我们到家的时候他已经走了。
By the time the doctor arrived the patient had died.
在医生到达时，病人已经死了。
By the time our teacher came in，we had started speaking English.
在老师进来前,我们都已经开始讲英语了。
by the time when got to the bus station，the bus had left.
在我们到达车站时,汽车早就开走了。
We had already left by the time they arrived.
那天他们到的时候，我们已经先走了。
By the time we arrived, someone had grabbed all the good seats.
我们到达时，所有的好位子都给人占了。
She had slipped into a coma by the time she reached hospital.
到医院时，她已陷入昏迷。
By the time he woke up, remembered the race and started running, he saw that the tortoise had already reached the finish line and won.
（兔子）醒来时，他想起了比赛，于是开始跑了起来，却发现乌龟早已到达终点，赢得了比赛。
By the time he was fourteen years old, Einstein had learned advanced mathematics all by himself.到14岁的时候，爱因斯坦就已经自学完了高等数学。
He had left by the time we reached home.
当我们到家的时候他已经走了。
London was an hour away and by the time I arrived the operation had already been performed.
伦敦离这里有1小时路程，当我赶到时，手术已经完成了。
By the time the tests took place, the athletes had had a full 17 hours notice.
到检测开始时，离运动员得到通知已经整整17个小时了。
2.如果从句中的谓语动词为一般现在时/或现在完成时（表示将来），那么主句中的谓语动词常为将来完成时，表示“截止到将来某一时间为止，主句动作将已经完成”
主句用will have done+by the time+从句用一般现在时态
By the time you get back，I shall have finished the work。
到你回来时，我将已经把活做完了。
By the time this gets into print, they'll already have left the country.
这篇东西发表的时候，他们将已经离开这个国家了。
We will have already left by the time they arrive.
一会儿等他们来的时候，我们就将离开了。
We will have finished the work by next month.
到下个月我们就会干完了这工作。
By the time you get back，I shall have finished the work。
到你回来时，我将已经把活做完了。
By the time John finishes his homework, his classmates shall have left to play football.到约翰做完作业时，她的同学将已离开去伦踢足球了。
He has read about 40 pages of the book by now.
现在这本书他已读了大约40页。
二)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。也可以根据具体情况选择需要的时态。
By the time we arrived the meeting was over.
我们到达时，会议已结束了。
By the time you get there the meeting will be over.
等你到了那里的时候，会议就该结束了。
By the time I arrived on the scene, it was all over.
我来到现场时，一切都已结束。
By the time I saw the job advertised it was already too late to apply. 等到我看到招聘广告的时候，已经太晚了，错过了应聘时机。
Often by the time they do accept the truth they are past being able to put words to feelings.
往往等他们真正接受事实时，他们已无法用语言形容自己的感情了。
By the time she'd twigged what it was all about it was too late.
等到她把一切都想通时，已为时太晚。
By the time ambulancemen arrived he was unconscious
救护人员到达时他已经不省人事了。
By the time the war was over , death and suffering were to be seen everywhere.
在战争结束的时候，到处可见死亡和饥饿。
You were a total failure if you hadn't married by the time you were about twenty-three.
如果到了23岁左右还没结婚，你就是个彻底的失败者。
She was already a famous model and pin-up by the time she made her film debut.
步入影坛时，她已是名模和海报女郎了。
By the time you get there the meeting will be over.
等你到了那里的时候，会议就该结束了。
By the time I arrived on the scene, it was all over.
我来到现场时，一切都已结束。
She was tired and out of sorts by the time she arrived home.
她回到家里，又累又烦。
By the time we got back from dinner, Nona was already in bed.
我们吃完饭回来时，诺娜已经睡下了。
By the time she was fifteen Maria was already running after men twice her age.
玛丽亚15岁的时候就已经在追求年龄比自己大一倍的男人了。
Her singing career was all washed up by the time she was 27.
她到27岁时歌唱生涯就告终了。
By the time he'd fixed the leak, I was into him for$ 500.
他补好漏洞时，我就该付给他500元。
By the time we had made landfall the boat looked ten years older!
等到我们登陆时，这艘船看似已老了10年！
It was well after midnight by the time Anne returned to her apartment.
安妮回到寓所的时候早就过了午夜。
Scott was obviously inebriated by the time the dessert was served.
到了上甜点的时候，斯科特显然已经喝醉了。
It was dark by the time she got home.
她回到家时天已经黑了。
By the time he died, he was a millionaire.
到他去世的时候，他已经是一位百万富翁了。
By the time the bus came so many people were waiting that it was a free fight to get on it.
公共汽车来的时候，等车的人很多，成了一场挤车的混战。
He was out of breath by the time he reached the top.登上顶端时，他气喘吁吁。
By the time I get home, I'm too tired to do anything active.
我到家时累得无法动弹。
Denise hopes to be back at work by the time her daughter is one.
丹尼丝希望等女儿满周岁就回去工作。
By the time he's twenty he'll know everyone worth knowing in Washington.
到20岁时，他就会认识华盛顿所有值得认识的人。
His ideas should be more advanced by the time the Committee meets in Edinburgh in October.
到委员会10月份在爱丁堡开会时，他的观点应该更为成熟了。
Cats sleep by day and hunt by night.
猫白天睡觉，夜里捉老鼠。
Do you like to swim by moonlight?
你喜欢在月光下游泳吗？