Use ‘in’ with months, years and periods of time such as decades or centuries:
- in January
- in 1978
- in the twenties
When does the school year begin in your country? – In mine it begins IN September.
Use ‘in’ a period of time in the future to express that an action will occur after that amount of time:
- in a few weeks
- in a couple of days
Use ‘at’ with an exact time:
- at six o’clock
- at 10.30
- at two p.m.
When do you eat lunch? – I usually eat it AT noon.
Use ‘on’ with days of the week:
- on Monday
- on Fridays
Use ‘on’ with specific calendar days:
- on Christmas day
- on October 22nd
When is your birthday? – Mine is ON October 12.
in the morning / afternoon / evening – at night
We say in the morning, afternoon or evening BUT we say ‘at night’.