Prepositions and Time Words

In

(year, month)

In 1989, in December

On

(day, date)

On monday, on Dec. 14, 2001

At

(time)

At 7:00, at 8:30

During

(decade, long time period)

During the 1960s, during the 20th Century

When did you eat your breakfast?

I ate my breakfast at 9:00.

When were you born?

I was born in 1979.

When is your birthday party?

My birthday party is on Friday.

When will you graduate?

I wil graduate in June.

How long have you been in the U.S.?

I have been here since 1999/for two years.

How long were you in California?

I was in California for three weeks.

How long will you be in Maine?

I will be there for a month.

In + (amount of time) usually refers to the future:

I will see you in two days (from now).

But it can also indicate a length of time:

I finished the job in two hours.

I called her two weeks ago.

She returned my call five minutes ago.

When

When I was in high school, I had a car.

As soon as

As soon as I got to the theater, I looked for a seat.

Once

Once I finish my geometry, I will start studying chemistry.

The moment (that)

The moment (that) I saw her, I knew who she was.

Before

Before my husband left, I had already packed his bags.

After

After she eats her dinner, Ms. Warner will go shopping.

By the time

By the time I get to Denver, I will have traveled 200 miles.

Until

I cleaned the house until my wife came home.