I know I've been asking a lot of questions lately about tenses. But please bear with me here.     NASA scientists have decided to delay the space shuttle's launch in order to determine whether recently repaired parts will cause damage if they break off in orbit.   So for the above example, I know will is correctly used. But I don't understand why there needs to be Present Perfect. Since this happened in the past shouldn't there be Simple Past?   Is this because NASA's decision is continuing into the present?
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Non-na­tive speak­ers of­ten get con­fused about what the var­i­ous tens­es  and as­pects mean in English. With in­put from some of the folk here I've put to­geth­er a di­a­gram that I hope will pro­vide some clar­i­ty on the mat­ter.  I of­fer it as the first an­swer to this ques­tion. Con­sid­er it a liv­ing doc­u­ment. In­put is wel­come, and good sug­ges­tions will be  in­cor­po­rat­ed in­to the di­a­gram.    No­ta bene: What this is not is a dis­cus­sion of whether there are  more than two tens­es in English. , to which this ques­tion is not in­tend­ed to sup­ply ar­gu­ments one way or the oth­er.  Here, the aim is to pro­vide an overview of what con­struc­tions English-speak­ing peo­ple use for con­vey­ing in­for­ma­tion about ac­tions re­fer­ring to past, present, and fu­ture, and to pro­vide it first and fore­most to pre­cise­ly the peo­ple who are like­ly to use "tense" as a catch-all term in their search, rather than to lin­guists who know bet­ter.  Break­ing News There is now an ex­cel­lent ELU blog ar­ti­cle ti­tled  . It is high­ly rec­om­mend­ed read­ing.
113209
The simple past tense indicates that an activity or situation began   and ended at a particular time in the past.      The present perfect expresses the idea that something happened (or   never happened) before now, at an unspecified time in the past.The   exact time it happened is not important. It also expresses the   repetition of an activity before now. The exact time of each   repetition is not important.   Even though I understand the explanation above, I can't figure out: If the present perfect states the idea that something happened in the past, why not use the simple past?  For example, would you please explain the following sentence to tell the difference between these two tenses?         The plane crashed there.    The plane has crashed there.      What is the biggest difference between them?
66036
"These days" express the period around now. Then, I wonder, why is used the Present Simple in the following sentence?:   These days I travel a lot.  I’m spending more and more time away from home. (Considering the rule given above, I would say: These days I am travelling a lot.)   I've also come across the sentence where both  tenses are considered correct:   These days, more and more people prefer / are preferring to retire    early.   So, is it optional whether we use present simple or continuous with "these days"?
24216
In Korea, we learned that we should use the past tense when the subject is an historical event, as in "The Korean war broke out in 1950."  However, I think that when the event continues to affect the present (now), we should use the present perfect.  So I think that we can say 'The Korean war has broken out in 1950.'  Am I right?
7181
At the dentist's:     I was on time for my dentist's appointment, but the dentist was still busy with another patient, so I sat in the waiting room and read some of the old magazines lying there. All the while I was wondering whether to leave and come back another day .   Why past simple here and not past continuous? To me both actions are in progress they are not completed
96818
I have a question about violating verb tenses. I was taught that you can't use present perfect (or continuous) and past simple within a sentence. You either have to use present perfects (or continuous) with present perfects (or continuous), and past simples with past simples. But I've found this not to be true, so I'm a bit confused.   Here is an email one of my native American friends sent me.     Hey, it's been such a long time since we last emailed each other. Thanks for sending me an email! Getting that email was such a pleasant surprise, because I was just thinking how I've been wanting to send you an email as well.   What confuses me the most is the last part. How can you say that you were thinking about how you have been wanting to do something?   I was taught that this is wrong: "he has decided to go hiking, so I went hiking as well." But I'm assuming that my friend's email is correct, since he IS a native speaker.   So, this is what I'm thinking: I can't say present perfect (or continuous) + past simple, but I can say past simple + present perfect (or continuous).   This violates verb tenses:     "he has decided to go hiking, so I went hiking as well."    But this doesn't:     "I went hiking because he has decided to go hiking."   Are there instances where present perfect (or continuous) + past simple or vice versa is allowed and correct?  EDIT:  This is a difficult concept for me to grasp. But thank you for all your help, because I'm learning a lot. There are many sentences that don't make sense to me. I came across this sentence today:     "[I think this is inferred: During those days,] We've watched the movie many times. I really wanted this life to continue."   I'm not sure what the present perfect is doing here. I don't think it is being used for describing what a person has done before, like "I've seen that movie before". Why is it not simply "We watched the movie many times. [It was so good that] I really wanted this life to continue"?
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Recently, I came across this sentence "Before I'd had a chance to look at the letter, my sister ran up and pulled them out of my hand!" (it's in the book "destination B1 grammar &amp; vocabulary with answer key" unit 5 exercise F)   The word "Before" mean "my sister ran up" happened before "I'd had a chance" But the tense told me the opposite. Because "I'd had a chance" is in past perfect tense, so it must happened before "my sister ran up".   could you explain me why they use tense like that. and can I just use past simple tense in both parts of this sentence?
17149
I have never had this problem before. But after seeing some questions posted on ELU, I started to doubt. I have been through links1, pages of grammar books2, a lot of questions3 posted here and ELU. I now still can't seem to understand how the past perfect is exactly used. The references sometimes even contradict each other.  What I had understood so far was      The past perfect is not necessary if we are not 'going back' to the earlier past, and simply moving from one event to another.   but I then saw a lot of other 'rules' including      If the sequence is clear, the past perfect is not needed.   which is slightly different, less 'narrow' and can be applied in more situations than the first ruleA, and      The past perfect is optional only when talking about an action at a specific time.   This is confusing. Can anyone here clarify things out please?    A For example, for  Doing the survey [completed] -&gt; Showing the result      We showed the result of the survey we did.      If the second rule is applied, the sentence above is fine (the sequence is clear), but not if the first rule since we are not moving from any event to the next and possibly even going back.    1  and   2 Practical English Usage (2005) by Michael Swan, Collins Cobuild Student's Grammar (1991). Upper-Intermediate Cutting Edge.  3 including , , ,  etc.
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Which tense should I use in the following example?  Is it OK to use the Past Perfect Continuous if I want to explain to someone that I had been working in some company for 10 years, without mentioning - before I finally quit, or maybe I should use the Past Perfect - I had worked in that company for 10 years… but also without mentioning - before I moved to… ???  Thanks!
457
I am not sure if we can use the present for future events. I know we can use the historical present for past event, but I am not sure if we can use the present for future events.  Here's an example sentence where the present is used for future events:     You should ask God "What is the meaning of life" when he judges your   soul.   Is judges being in the present tense ok in this case?
68248
I would like to know if there are any other tenses or grammatical structures to use for speaking about the future apart from will (perfect tense included), going to, simple and continuous present.  I mean not the obvious ones. For example, simple present (I could never have imagined it could be used for the future).     My mom arrives tomorrow.   I go to the doctor at 4 o'clock this afternoon.
118007
Which is preferable, simple past or present perfect, in situations like this one: I had a conversation with my friend and we planned to do something; shortly afterwards I call him back to announce the accomplishments. My biggest doubt about simple past is that perfect aspect is used to indicate past action (accomplishment) with current relevance, at the same time I'm not sure if I'm allowed to use present perfect, because there's a gap between accomplishing and the current moment, which is a characteristic of simple past.
22594
A few days back, I asked a question - why in reported speech is the present perfect tense sometimes not back shifted to the past perfect tense ? For example:     He said that he has painted the door.   Someone said - "if the situation is still relevant and the results of it can be seen, heard or felt then the present perfect tenses are not back shifted to past perfect tenses." And this was all about indirect speech, and I totally agree with what was said.  Now let's take a case which is not indirect speech. For example:     1) He noticed that he has finished painting the house.   My question is, is this sentence correct under the condition that finishing the painting has some present relevance ?     2) The president learned that the earthquake has caused havoc across   the country.   My question is, is this sentence correct under the condition that the earthquake has recently come and the effects of it can still be seen ?     3) I realized that he has left his wallet.      4) It was unclear that she has painted the door.   Are these 4 sentences correct or do I need to use 'had' in place of 'has' ?
110048
I am now reading  book and have noticed a couple of cases of weird (for non-native speaker) future tense usages.   The point of the kata is to train your fingers and your brain. I'll do a kata or two every day, often as part of settling to work. I might do it in Java, or in Ruby, or in Clojure, or in some other language for which I want to maintain my skills.`   The phrase about doing a kata or two every day looks perfect for Present Simple. Why does the authoer use Future Simple instead?   However, a professional also knows that there will be times when he will fail, his risk calculations will be wrong, his abilities will fall short; he'll look in the mirror and see an arrogant fool smiling back at him.   Shouldn't we use Present Simple after when/if in this kind of cases? I am especially curious about this case as sometimes I forget to switch to Present Simple after if/when and I thought it is a critical error (which I didn't expect to see in a book).
58862
I know the rule is to use past simple when you specify the time when the described action happened, but I strangely dislike this sentence and I'm not sure if the rule applies:   "It's the best movie I saw this year".  Shouldn't it be: "It's the best movie I've seen this year"?  Please, could you justify your answers? Thank you in advance!  Cheers
105394
I thought we can use perfect infinitive construction to talk about plans which didn't happen. For instance:     I was to have started work last week, but I changed my mind.   But what about that construction:     I'm sorry to have disturbed you.   Both two these examples were taken from M. Swan from the regarding sections.
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My friend asked me just today, "Hey, how are you?"        I said, "Tired, sleepy, and can't concentrate on my work."      He then asked, "Why so?"   Here is where the interesting part starts.       I said, "I have had a headache yesterday"   He said that I should have said "I had a headache yesterday" instead of "I have had a headache yesterday"  But all grammar books say that with Present Perfect + Past Tense we mean an action that continues into the present; has consequences in the present.  I didn't want to just tell the fact that I had a headache but I implied that that was the reason I was "Tired, sleepy, and can't concentrate on my work."  Who is right?