Unit 12. When...? and How long...? For and since

Campare 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.

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

We use for when we say a period of time. (two hours, six weeks etc.) - I've been waiting for two hours. - Sally's been working here for six mounths. - I haven't seen Tom for three days.

We use since when we say the start of a period. (8 o'clock, Monday, 1985 etc.) - I've been waiting since 8 o'clock. - Sally's been working here since April. - 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.

We say 'It's (a long time / two years etc..) sine 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 th cinema.
  = We hanve'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 aee Joe?
• How long is it since Mrs Hill died?
  = When did Mrs Hill die?