By the time 用法详解•by the time意为“到……时候（为止）”，是一个介词短语，在句中经常起连词作用，引导时间状语从句。
它的主要用法如下：• 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“截止到从句动作发生时，主句动作已经完成，即过去的过去”。
例如：By the time he returned home，the rain had stopped.•By the time I got to the station，the train had already gone。
• 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”。
By the time you get back，I shall have finished the work.•By the time I graduate next year, I will have lived here for 5 years.•By the time of next term , we will have learned 3000 words.• 3. 如果主句动作不强调已经完成，只是说明某个时候的状况，（主句是be的系表形式或者是表示像know, find, believe等表示认知的持续性动词，则往往用一般时态，不用完成时态。
）此时主句不用完成时，而应根据实际需要选用适当的时态，此时by the time相当于when。
例如：•He was out of breath by the time he reached the top.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。
•By the time he went abroad, he was fourteen.出国那年他14岁。
•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。
这里没有“死亡和饥饿”已经完成的意思，只是描述当时这个时间点的状况。
所以用过去时。
•巩固练习：• 1. （2005天津卷）By the time Jane gets home，her aunt _____for London to attend a meeting.A. will leaveB. leaves• C. will have left D. left• 2. By the time you have finished this book, your meal ___ cold.(2012四川卷)• A. gets B. has got C. will get D. is getting• 3. （2009北京卷）When I talked with my grandma on the phone，she sounded weak，but by the time we _____ up，her voice had been full of life.A. were hangingB. had hung• C. hung D. would hang• 4. ―Did you see Xiao Li at the party？―No，_____by the time I arrived.A. she’d leftB. she’s left• C. she was left D. she must leave5. By the time I saw the angry expression on his face，I_____ what I had to face.A. knewB. have known• C. would know D. had known6.（2008四川卷）The telephone_____，but by the time I got indoors，it stopped.A. had rungB. was ringingC. ringsD. has rung•7.（2008山东卷）By the time he realizes he _____into a trap，it’ll be too late for him to do anything about it.A. walksB. walkedC. has walkedD. had walked情态动词用法总结如下表学法提炼If they _________ to do this work, he might do it some other way.A. wereB. shouldC. willD. can2. I was told yesterday that the company _________ me to Rome next week for a business conference.A. should have sentB. were going to sendC. should be sendingD. should send3. Let’s take a walk, ________?A. will weB. don't weC. do weD. shallwe4. He was a good swimmer so he _________ swim to the river bank when the boat sank.A. couldB. mightC. shouldD. was able to5. I went to the doctor's yesterday, I had to wait for half an hour before he ________ see me.A. canB. mayC. mightD. could6. ---- _________ this book be yours? ---- No, it ________ not be mine. It ________ be his.A. Can, must, mayB. May, might, mustC. Can, may, mustD. Must, can, may7. ---- "We didn't see him at the lecture yesterday.”---- “He _________ it.”A. mustn't attendB. can't have attendedC. would have not attendedD. needed have attended8. They _________ the plane, or perhaps they have been prevented from coming for some reason.A. can have missedB. may have missedC. can have lostD. may have lost9. Since the ground is white, it _________ last night.A. had snowedB. must have snowedC. must be snowingD. must have been snowing10. You must be fifty, ________?A. mustn't youB. needn't youC. aren't youD. mayn't you11. You must have seen him off yesterday, _________?A. haven't youB. didn't youC. mustn't youD. needn't you12. ---- That must be a mistake.---- No .it _________ be.A. can'tB. isn't able toC. canD. was able to13. He had known the matter before you told him, so you _________ have told it to him.A. mustn'tB. can'tC. needn'tD. shouldn't14. How ________ so?A. dare you to sayB. dare you sayC. do you dare sayD. dare to say15. You are their teacher. You _________ care of them.A. should to takeB. might to takeC. ought to takeD. need to take16. She is studying medical science now but she _________ a lawyer.A. used to beB. would beC. wereY ou return the book now. You can keep it till next week if you like.A. can'tB. mustn'tC. needn'tD. maynot2. I wish I________ to the moon one day.A. can flyB. an able to flyC. could flyD. wasable to fly3. If my lawyer _______ here last Saturday, he _______ me from going.A. had been; would have preventedB. had been; would preventC. were; would preventD. were; would have prevented4. If it________ for the snow, we _______ the mountain yesterday.A. were not; could have climbedB. were not; could climbC. had not been; could have climbedD. had not been; could climb5. Without electricity human life ______ quite difficult today.A. isB. will beC. would have beenD.would be6. Jenny _______ have kept her word. I wonder why she changed her mind.A. mustB. shouldC. needD.would7. W e _______ last night, but we went to the concert instead.A. must have studiedB. might studyC. should have studiedD. would study8. —Could I borrow yourdictionary?—Yes, of course you ________ .A. mightB. willC. canD.should9. —If he ________ , he ________ that food.— Luckily he was sent to the hospital immediately.A. was warned; would not takeB. had been warned; would not havetakenC. would be warned; had not takenD. would have been warned; had nottaken10. I told Sally how to get here, but in fact, I _______ her, for she had been here a short time before.A. needn't tellB. didn't need to tellC. needn't have toldD. didn't need to have told。