UNIT 12 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. ¡ 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 et c.): ¡ I've been waiting since 8 o'clock. ¡ 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 I 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):

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.

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 .



C. We say:

¡ 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?)

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