| Saturday the weekend Monday morning breakfast New Year’s Day July the winter/the summer the twenty-first century lunchtime Thursday afternoon |
| AT | IN | ON |
| 12 o’clock | the morning | the 4th of July |
| night | ||
To help you remember which proposition of time to use, try to memorise this: on Monday, in winter, at that time
On= for specific days, in=for time periods, at= for specific times
Note: last month, every March, next day, this morning. We don’t use a preposition with some time expressions this/last/next/every morning, week, year etc.