General

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

Specific Time: "When?" (Use simple tenses.)

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 will graduate in June.

Ongoing Action

Mr. Barnes is watching television now.

While he was watching television, the phone rang.

He will be watching television tonight when his wife gets home.

Duration: "How Long?"

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.

Completed Action

I have finished my homework already. (before now)

After I had finished my homework, I started to cook dinner.

I will have finished my homework, when I start to cook dinner.

Notes:

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.

Ago follows time word(s) and is used to indicate the amount of time before the present:

I called her two weeks ago.

She returned my call five minutes ago.

Words indicating actions occurring at the "same" time (or nearly the same time)

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.

Words indicating actions occurring at "different" times

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.

See also:

Grammar : Prepositions

Grammar : Using Time Expressions

If you have questions or comments about this page, please contact us.