UNIT 13. 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 =====>|

two hours ago ---------------> now

for

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

Kelly 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
(8:00, Monday, 1999, etc.):

I’ve been waiting since 8:00.

|======== since 8:00 =====>|

8:00 -------------------> now

since

8:00
April
lunchtime
Monday
1985
we arrived
May 12
Christmas
yesterday

Kelly 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 in negative sentences):

They’ve been married (for) 10 years. (with or without for)
They haven’t had a vacation for 10 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:

They haven’t had a vacation in 10 years.

B

Compare When …? (+ simple past) and How long …? (+ present perfect)

A : WHen did it start raining?
B : It started raining an hour ago / at 1:00.

A : How long has it been raining?
B : It’s been raining for an hour / since 1:00.

-—————————–

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

A : How long have they known each other?
B : They’ve known each other { for a long time. / since they were in high school. }

C

We say “It’s(= It has) been a long time / two years, etc., since something happened?” :

It’s been two years since I saw Joe. (= I haven’t seen Joe for two years)
It’s been ages since we went to the movies. (= We haven’t gone to the movies for ages)

You can ask “How long has it been since …?”

How long has it been since you saw Joe? (= When did you last see Joe?)
How long has it been since Mrs. Hill died? (= When did Mrs. Hill die?)