Think in zoom levels. Use in for long periods: in May, in 2026, in the morning. Use on for days and dates: on Monday, on 3 June. Use at for exact times and moments: at 9:00, at noon, at night.
Our call is on Monday at 9:00.
Each word is a zoom level. In covers the widest periods, on zooms in to a single day, and at zooms all the way in to a point in time.
| in | Months, years, seasons, centuries, parts of the day: in May, in 2026, in summer, in the evening |
|---|---|
| on | Days, dates, special days: on Monday, on 3 June, on my birthday, on Christmas Day |
| at | Clock times, short moments, holiday periods: at 9:00, at noon, at lunchtime, at Christmas, at the moment |
| No preposition | next, last, this, every, today, tomorrow, yesterday: next week, this morning |
At night, but in the morning / afternoon / evening. And at the weekend (British English) or on the weekend (American English).
My birthday is in May.
Months, years, seasons, decades, centuries and parts of the day.
The exam is on 12 June.
Days of the week, dates, and special days like your birthday.
The train leaves at 7:15.
Clock times and short moments: at noon, at midnight, at the start.
She called me on Tuesday evening.
In the evening, but when the evening belongs to a particular day, the day wins: on Tuesday evening, on the morning of 5 May.
Common expressions worth learning as they are.
The shop opens _____ 9 o'clock.
Time and place, side by side.
Paste an email or an essay. Clarigram marks the mistakes you actually make, shows the rule behind each one as a picture, and builds your practice from them.
Both are correct. At the weekend is British English; on the weekend is American English.
At the end means at the final point of something: at the end of the film. In the end means finally, after some time: In the end, we stayed at home.
No: next Monday, last year, this morning. The word already says when, so in, on and at disappear.