at, on, 그리고 in의 비교:
They arrived at 5:00.
They arrived on Friday.
They arrived in October. / They arrived in 1998.
at은 시간에 대해 사용합니다:
at 5:00 at 11:45 at midnight at lunchtime at sunset
on은 날짜와 요일에 대해 사용합니다:
on Friday / on Fridays on March 12, 2002 on Christmas Day on my birthday
그리고 on the weekend, on weekends와 같이 주말에도 on을 사용합니다.
in은 months/years/seasons와 같은 기간에 대해 사용합니다:
in October in 1998 in the 18th century in the past
in (the) winter in the 1970s in the Middle Ages in the future
아래와 같은 표현에는 at을 사용합니다:
at night
at Christmas / at Easter
at the moment / at this time
at the same time
I don't like going out at night.
Do you give each other presents at Christmas?
Mr. Brown is busy at the moment / at this time.
Liz and I arrived at the same time.
아침, 오전, 오후, 저녁에 대해서는 in을 사용합니다:
in the morning(s) in the afternoon(s) in the evening(s)
I'll see you in the morning.
Do you work in the evening?
그러나 다음과 같은 표현에는 on을 사용합니다:
on Friday morning(s) on Sunday afternoon(s) on Monday evening(s)
I'll be at home on Friday morning.
Do you usually go out on Saturday evenings?
last/next/this/every앞에는 at/on/in을 사용하지 않습니다:
I'll see you next Friday. (not on next Friday)
They got married last March.
날짜와 요일앞에 on은 종종 생략되기도 합니다 (Monday / Mondays / Monday morning / March 12th 등):
I'll see you (on) Friday.
She works (on) Saturday mornings.
They got married (on) March 12th.
in a few minutes / in six months등과 같은 표현에서 in은 "~ [시간] 내에"로 미래의 시간을 의미합니다:
The train will be leaving in a few minutes. (= a few minutes from now)
Jack has left town. He'll be back in a week. (= a week from now)
She'll be here in a moment. (= a moment from now)
"in six months' time", "in a week's time" 등과 같은 표현도 사용합니다:
They're getting married in six months' time. (or ... in six months.)
어떤 일을 하는데 걸리는 시간을 이야기하기 위하여 in을 사용합니다:
I learned to drive in four weeks. (= It took me four weeks to learn.)