This unit shows you the meaning and use of after, at, before, by, for, from, in, on, since, to, until when we want to say when or how much time.


Monday comes before Tuesday. Tuesday comes after Monday.


at six o'clock/ half past three...

at midnight/ midday/ lunchtime

at Christmas/ Easter/ the weekend... (ALSO during)

on Friday/ the fourth of May/ New Year's Day/ Friday afternoon...

in the morning/ the late afternoon... (ALSO during)

in January/ Ramadan/ the first month... (ALSO during)

in spring/ summer/ autumn/ winter (ALSO during)

in 1989/ the 1960s/ the eighteenth century... (ALSO during)


I'll be there by six o'clock.
= I'll arrive at six or before.

I'll be there until six.
= I'll leave at six.

I won't be there until six.
= I'll arrive at six, not before.

By November, the weather had become very cold.
= Before November, it got colder, and it was very cold in November.

I'll be there from three to six.
= I'll arrive at three and leave at six.


I can see you in five minutes.
(starting after five minutes)

I can see you for five minutes.
(a five-minute talk)


I have known him since 1985.
I have known him for twenty-two years.

= It is 2007. We first met twenty-two years ago (in 1985).

NOTICE: We can use after, before, since and until before a subject and a verb:

We played football after we finished school.
We played football until it got dark.

We cannot use at, by, for, in and on in this way.

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Exercise 72.1
Exercise 72.2
Exercise 72.3