at + exact time
in + part of day
on + particular day
at + weekend, public holiday
in + longer period
1. Exact times
- I usually get up at six o'clock
- I'll meet you at 4.15
- Phone me at lunch time
In informal English, we say What time...?
(At what time...? is correct, but unusual.)
2. Parts of the day
- I work best in the morning
- three o'clock in the afternoon
- we usually go out in the evening
Exception: at night.
We use on if we say which morning/ afternoon/ etc we are talking about,
or if we describe the morning/ afternoon/ etc.
- See you on Monday morning
- It was on a cold afternoon in early spring...
3. Days
- I'll phone you on Tuesday.
- My birthday's on March 21st.
- They're having a party on Christmas Day.
In informal speech we sometimes leave out on (This is common in American English)
- I'm seeing her Sunday morning.
Note the use of plurals (Sundays, Mondays etc)
when we talk about repeated actions.
- We usually go to see Granny on Sundays.
4. Weekends and public holidaysWe use at to talk about the whole of the holidays at Christmas, New Year,
Easter and Thanksgiving (US)
- Are you going away at Easter?
We use on to talk about one day of the holiday
- It happened on Easter Monday.
British people say at the weekend. Americans use on.
- What did you do at the weekend?
5. Longer periods
- It happened in the week after Christmas
- I was born in March
- Kent is beautiful in spring
- He died in 1212
- Our house was built in the 12th Century
6. Expressions without prepositionPrepositions are not used in expressions of time before
next, last, this, one, any, each, every, some, all.
- See you next week.
- Are you free this morning
- Let's meet one day.
- Come any time
- I'm at home every morning.
- We stayed all day.
Prepositions are not used before yesterday, the day before yesterday,
tomorrow, the day after tomorrow?
- What are you doing the day after tomorrow?