Page 216 - Practical English Usage 3ed - Michael Swan, Oxford

208 for, since, in and from: time
1 for
We use for for duration - to say how long something lasts.
2
for + period of time
I studied the guitar for three years at school. That house has been empty for six months. We go away for three weeks every summer.
My boss will be in Italy for the next ten days.
To measure duration up to the present, we use a present perfect tense
(see 460), not a present tense.
I've known her for a long time. (NOT .' kn6ftJ herJ"-B,. a ltmg time.) We've lived here for 20 years. (NOT We UfJe here }'Br 26 years.)
A present tense with for refers to duration into the future. Compare: How long are you here for? (= Until when ...1)
How long have you been here for? (= Since when ...1)
We can often leave out for in an informal style, especially with How long ...? And for is not usually used before all.
How long have you been waiting (for)?
We've been here (for) six weeks. I've had a headJJche all day.
for and since with perfect tenses: the difference
For and since can both be used with a present perfect to talk about duration up
to the present. They are not the same. Compare: for + period
I've known her for three days. (NOT ••• sinee three dtlys.) It's been raining for weeks.
since + starting point
I've known her since Tuesday.
It's been raining since the beginning o f the month.
With a past perfect, for and since refer to duration up to a particular past moment.
She'd been working there for a long time. (NOT ••• sinee a ltmg time.) She'd been working there since 1988.
in after negatives and superlatives (ArnE)
After negatives and superlatives, in can be used to talk about duration. This is especially common in American English.
I haven't seen him for/in months.
It was the worst storm for/in ten years.
from and since
From and since give the starting points of actions, events or states: they say
when things begin or began. /rom/since + starting point
3
4
I'll be here from three o'clock onwards.
for, since, in and from: time 208
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