GUIDE ENGLISH GRAMMAR BOOK

PAGE 297
227 Prepositions of time
c
d
During is a preposition; while is a conjunction.
Someone told me the news during the tea break.
Someone told me the news when/while we were having a cup of tea.
We can also use over for a whole period of time.
Over the next few days, Simon and Kay saw a lot of each other.
Over a period of two months there were a hundred sightings of UFOs.
NOTE
The adverb over means 'finished'.
This programme will soon be over.
5 For and since
a
We use for with a period of time to say how long something continues.
Rachel plays computer games for hours on end. NOT during hours • (4)
I once stayed at that hotel for a week.
I just want to sit down for five minutes.
NOTE
We do not normally use for before a phrase with all or whole.
It rained all day/the whole day.
b
We often use for and since with the perfect to say how long something has
continued or when it started.
Giles has worked here for ten years now.
We haven't been to the theatre for months.
We've been waiting for twenty minutes.
The Parkers have lived here since 1985.
I haven't seen you since September.
We've been waiting since twelve o'clock.
We use for + length of time and since + time when.
for two years for a week for two days for a few minutes
since 1990 since last week since Monday since half past two
NOTE
a We can sometimes leave out for in informal English.
We've been waiting here twenty minutes.
b We use during for a period which is a definite time. • (4)
During the last ten years Giles has been promoted at least three times.
c Compare these sentences.
I've been here (for) ten minutes. I'll stay (for) ten minutes.
I've been here since twenty to four. I'll wait until four o'clock. • (6)
I arrived ten minutes ago. I'm leaving in ten minutes.
c
d
We use the adverb ago for a past action at a time measured from the present.
Ago comes after the length of time.
Giles joined the company ten years ago. (= ten years before now)
We last went to the theatre months ago.
We use the adverb before for a past action measured from the more recent past.
Giles left the company last year. He'd started work there ten years before.
(= ten years before last year)