When...? and How long...? For and since

10 Unit

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 Joe and Carol known each other? B: They ve known each other since they were at school.

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

for two hours a week 20 minutes 50 years five days a long time six months ages	since 8 o'clock 1977 Monday Christmas 12 May lunchtime April they were at school
Sally's been working here for six month not ' since six months). I haven't seen Tom for three days. (not 'since three days').	Sally's been working here since April. (from April until now). I haven't seen Tom since Monday. (from Monday until now).

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.

We say 'It's (a long time / two years etc.) since'something happened':

• It's two years since I last saw Joe. ( I haven't seen Joe for two years / the last time I saw Joe was two years ago)

• It's ages since we went to the cinema. ( We haven't been to the cinema for ages)

The question is How long is it since...?

• How long is it since you last saw Joe? ( When did you last see Joe?)

• How long is it since Mrs Hill died? ( When did Mrs Hill die?)