012 : for and since when … ? and how long … ?

   A   

We use for and since to say how long something has been happening.

 

We use for + a period of time (two hours, six weeks etc.): I've been waiting for two hours. for: two hours, 20 minutes, a long time, six months, a week, ages, five days, 50 years, years Sally has been working here for six months. (not since six months) I haven't seen Tom for three days.

We use since + the start of a period (8 o'clock, Monday, 1999 etc.): I've been waiting since 8 o'clock. since: 8 o'clock, April, lunchtime, Monday, 2001, we arrived, 12 May, Christmas, I got up Sally has been working here since April. (= from April until now) I haven't seen Tom since Monday.

It is possible to leave out for (but not usually in negative sentences):

• They've been married (for) ten years.  (with or without for)
• They haven't had a holiday for ten years.  (you must use for)

We do not use for + all ... (all day / all my life etc.):

• I've lived here all my life. (not for all my life)

You can use in instead of for in negative sentences (I haven't ... etc.):

• They haven't had a holiday in ten years. (= for ten years)

 

 

 

   B   

Compare when ... ? (+ past simple) and how long ... ? (+ present perfect):

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A: When did it start raining?
B: It started raining an hour ago / at 1 o'clock.

 

A: How long has it been raining?
B: It's been raining for an hour / since 1 o'clock.

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A: When did Joe and Carol first meet?
B: They first met a long time ago / when they were at school.

 

A: How long have they known each other?
B: They've known each other for a long time / since they were at school.

 

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   C   

We say:

 

It's (= It is)	a long time six months (etc.)	since something happened
It's been (= It has been)

• It's two years since I last saw Joe.  or  It's been two years since ...
  (= I haven't seen Joe for two years)
• It's ages since we went to the cinema.  or  It's been ages since ...
  (= We haven't been to the cinema for ages)
• How long is it since Mrs Hill died?  or  How long has it been since ... ?
  (= When did Mrs Hill die?)