Rules
- at for a PRECISE TIME
- in for MONTHS, YEARS, CENTURIES and LONG PERIODS
- on for DAYS and DATES
| PRECISE TIME | MONTHS, YEARS, CENTURIES and LONG PERIODS | DAYS and DATES |
|---|---|---|
| at 3 o’clock | in May | on Sunday |
| at 10.30am | in summer | on Tuesdays |
| at noon | in the summe | on 6 March |
| at dinnertime | in 1990 | on 25 Dec. 2010 |
| at bedtime | in the 1990s | on Christmas Day |
| at sunrise | in the next century | on Independence Day |
| at sunset | in the Ice Age | on my birthday |
| at the moment | in the past/future | on New Year’s Eve |
Expressions
| at | in | on |
|---|---|---|
| at night | in the morning | on Tuesday morning |
| at the weekend* | in the mornings | on Saturday mornings |
| at Christmas*/Easter | in the afternoon(s) | on Sunday afternoon(s) |
| at the same time | in the evening(s) | on Monday evening(s) |
| at present |
Note that in some varieties of English people say “on the weekend” and “on Christmas”.
Examples
- I have a meeting at 9am.
- The shop closes at midnight.
- Jane went home at lunchtime.
- In England, it often snows in December.
- Do you think we will go to Jupiter in the future?
reference:
englishclub