For and Since

Both for and since answer the question “how long?” but they work differently. For takes a period of time. Since takes a starting point.

For + a Period of Time

Use for when you describe how long something lasts. You give a duration — a stretch of time with no fixed start or end.

• We’ve been waiting for two hours.
• Sally has been working here for six months.
• I haven’t seen Tom for three days.

for + period
two hours
20 minutes
five days
six months
a long time
ages
50 years

Since + a Starting Point

Use since when you name the moment something began. The action started at that point and continues now.

• We’ve been waiting since 8 o’clock.
• Sally has been working here since April.
• I haven’t seen Tom since Monday.

since + starting point
8 o’clock
lunchtime
Monday
April
12 May
2001
Christmas
we arrived
I got up

Do not mix them up. You say for six months, not since six months.

Leaving Out “for”

You can often drop for in positive sentences:

• They’ve been married for ten years. = They’ve been married ten years.

But keep for in negative sentences:

• They haven’t had a holiday for ten years. (you need for here)

You can also use in instead of for in negatives:

• They haven’t had a holiday in ten years. (= for ten years)

“For” with “all”

Do not use for before all day, all my life, etc. Just use all directly:

• I’ve lived here all my life. (not for all my life)

When…? vs. How long…?

When…? asks about a point in the past and takes the past simple. How long…? asks about duration up to now and takes the present perfect.

Question	Answer
When did it start 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 Kate first meet?	They first met a long time ago.
How long have they known each other?	They’ve known each other for a long time / since they were at school.

At work, the same pattern applies:

• When did you join the company? — I joined in 2019.
• How long have you worked here? — I’ve worked here for six years / since 2019.

It’s … since …

You can express the same idea another way with it’s (been) … since …:

• It’s two years since I last saw Joe. (= I haven’t seen Joe for two years.)
• It’s been ages since we went to the cinema. (= We haven’t been to the cinema for ages.)
• How long is it since Mrs. Hill died? (= When did she die?)

Quick Self-Check