Using in, on, at for time expressions
Preposition + time expression (in March / on Friday / at 8 pm)
Use the same preposition; negate the verb (We don't meet on Sunday)
Question word + preposition if needed (When do you meet? At 6?)
💡 American English often uses on the weekend; British English at the weekend
✓We have class on Tuesday.
✗We have class in Tuesday.
Use on for days.
✓He was born in 1999.
✗He was born on 1999.
Use in for years.
✓The meeting starts at 9:00.
✗The meeting starts on 9:00.
Use at for clock times.
✓They travel in winter.
✗They travel on winter.
Use in for seasons.