As explained in full in The English Tenses Practical Grammar Guide, the perfect forms (including simple perfect and continuous perfect forms) can be used with a future meaning in English. The simple perfect tense with future meaning shows something has not been completed yet, but will be completed at a certain point in the future: I will have finished by tomorrow. The continuous perfect tense is used to tell us how long something has been occurring for at a certain point in the future: I will have been living in Brighton for 8 years this summer.
Simple perfect forms in the future
To use simple perfect tenses in the future, we replace the bare infinitive (main verb) with have + past participle. For instance, I will do it would be I will have done it.
| Subject | will / shall / be going to | have + past participle | |
|
Nobody She |
is going to won’t |
have prepared. have arrived |
before you. |
These perfect tense forms for future tenses view things from a particular point in the future as already having taken place or as having been completed.
It is often expressed using the terms by or before.
For example:
She will have finished by 6.00.
(She will finish between now and 6 – but has not already finished).
The perfect continuous form of future tenses
To use the perfect continuous for a future meaning, replace the bare infinitive (main verb) with have been + an –ing form. For instance I will learn English could be I will have been learning English for two years this July.
| Subject | will/ shall / be going to | have been + ing form of verb |
| He | will | have been living in Ghana for 40 years next July. |
We use this to view a particular point in the future when we are interested in how long something has been happening. It is often expressed with for.
She’ll have been working there for over twenty years when she retires.
Note there are exceptions when we often use simple forms, instead of perfect forms, for this meaning.
For example:
He’ll have known her for two years when they get married. (Not He’ll have been knowing her.)
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Dear Mr Williams,
Why can’t we use Present Perfect continuous tense (He’ll have been knowing her for 2 years) in the last sentence if we focus on how long has been something happening ?
Thank you and I look forward to hearing from you soon.
Sincerely,
Christine
Hi Christine,
This is to do with the verb choice – ‘to know’ is not considered an ongoing process, so once we know someone/something we treat it like it a completed action – “He’ll have known her for 2 years.” (i.e. It will have been 2 years since he met her.) I hope this clears it up!
Hi!
By the time I graduate , I will have been living here for 2 years.
By the time you get married, I will have been doing this job for 5 years.
What does mean by” By the time” ?
Second question: in April ,I will have been preparing for civil service exam for 5 months .
Why In April is considered wrong here .don’t” In April” indicate towards future time
Hi Sana,
With ‘by the time’ we essentially mean ‘before/at the time’, or otherwise that at the time mentioned the action/event will become true. It’s a bit like saying, “When I graduate, I will have lived here for 2 years.”
The problem with your second sentence is the preposition “in”; with a month, it would suggest the action is happening within that month, while your sentence indicates an ongoing action for 5 months. So you need to say “By April, I will have been preparing for 5 months.”
Phil