Expressing dates and times: on Monday, in January, at 3 o'clock
Preposition + time expression
Same structure
What time...? When...? What date...?
💡 No preposition with: today, tomorrow, yesterday, this/next/last + time.
✓I'll see you on Monday.
✗I'll see you in Monday.
ON for days of the week.
✓She was born in 1990.
✗She was born on 1990.
IN for years.
✓The meeting is at 2:30.
✗The meeting is on 2:30.
AT for specific times.