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

When ...? (+past simple)

How long...? (+present perfect)

When did it starting raining?

It started raining an hour ago/at 1 o’clock.

How long has it been raining?

It’s been raining for an hour/since 1 o’clock.

When did Joe and Carol first meet?

They first met a long time ago/when they were at school.

How long have Joe and Carol known each other?

They’ve known each other for a long time/since they were at school.

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.) We use since when we say the start of a period (8 o’clock, Monday, 1985 etc.)

For

two hours, 20 minutes, five days, six months, a week, 50 years, a long time, ages

Since

8 o’clock, Monday, 12 May, April, 1977, Christmas, lunchtime, they were at school

Sally’s been working here for six months.

Sally’s been working here since April.

I haven’t seen Tom for three days.

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’)

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 when 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?)