Use on with days.
- I met him on Friday.
- My birthday is on May 18th.
- We are having a small party on Christmas day.
Use at with clock times and other expressions of time such as noon, night and midnight.
- The train departs at 6.30.
- We usually have dinner at 9 o’clock.
- I will meet you at noon.
- Phone me at lunch time.
Use in with other parts of the day and with months, years and seasons.
- We usually go out in the evening.
- I saw him in the morning.
- I was born in May.
- Trees shed their leaves in autumn.
- Days are short and dark in winter.
- I take a nap in the afternoon.
- They got married in 1996.
- This house was built in 1972.
Other prepositions indicating time
In English, we use several prepositions to show time. The most common among them are: since, for, by, during and within. The sequences from-to and from-until are also used to talk about time.
- We have lived in this city since 2007. (We arrived in this city in 2007 and have lived here ever since.)
- She has been gone since Tuesday. (She went on Tuesday and has not returned yet.)
- I am going to Vienna for two weeks. (I will spend two weeks there.)
- I work from nine to six.
- I will be here from three o’clock onwards.
- The program lasted from 3 to 6. (Beginning at 3 and ending at 6)
- It rained during the night. (For a certain period of time in the night)
- We must finish the work within a year. (= No longer than a year)