At, On, In (Time)
Choosing at, on, or in when talking about times, days, dates, months, and longer periods
The Basic Rule
Each preposition matches a different size of time period:
| Preposition | Used for | Examples |
|---|---|---|
| at | a point in time (clock times, named moments) | The meeting starts at 9 a.m. / Let’s grab coffee at lunchtime. |
| on | days and dates | The deadline is on Friday. / She joined the company on 3 March 2021. |
| in | longer periods (months, years, seasons, centuries) | We launched the product in September. / He started his career in the 1990s. |
At — Clock Times and Named Moments
Use at when you are pointing to a specific moment on the clock or a recognized time of day.
- The conference call is at 2.30.
- I usually check my emails at midnight.
- Let’s meet at sunset — the terrace has a great view.
Fixed Expressions with At
| Expression | Example |
|---|---|
| at the moment / at present | We’re not hiring at the moment. |
| at the same time | Both teams submitted their reports at the same time. |
| at the weekend(s) | Do you ever work at the weekend? |
| at Christmas / at Easter | The office closes at Christmas. |
| at night | The factory runs at night to meet demand. |
Note the difference between at night (nights in general) and in the night (one particular night):
- Security guards patrol the building at night. (every night, as a routine)
- The server crashed in the night, so we lost some data. (one specific night)
On — Days and Dates
Use on when the time expression includes a day of the week, a calendar date, or a special day.
- The training session is on Wednesday.
- She was promoted on 15 January.
- We always have a team lunch on New Year’s Day.
Note: at Christmas (the holiday period) but on Christmas Day (the specific date, 25 December).
Morning / Afternoon / Evening + a Day
When you combine a part of the day with a specific day, the day wins — use on:
| Without a day → in | With a day → on |
|---|---|
| I’ll send it in the morning. | I’ll send it on Monday morning. |
| We train new staff in the afternoon. | We train new staff on Thursday afternoons. |
| I prefer to study in the evening. | The team dinner is on Friday evening. |
In — Months, Years, Seasons, Centuries
Use in for any period longer than a single day.
- Budget reviews happen in March.
- The branch opened in 2019.
- Sales tend to drop in winter.
- This technique was first used in the 20th century.
No Preposition: last, next, this, every
Drop at, on, and in before last, next, this, and every.
- I’ll finish the report next Friday. (not
on next Friday) - We hired three people last month. (not
in last month) - The system goes down every Sunday for maintenance.
- Are you free this afternoon?
You can also drop on before days in everyday speech:
- See you Friday. (= See you on Friday.)
- I don’t work Monday mornings. (= I don’t work on Monday mornings.)
In + a Period of Time = “from now”
Use in + a length of time to say when something will happen, counting from now.
- The client will be here in ten minutes. (= ten minutes from now)
- Your new badge will be ready in a couple of days.
- She’s transferring to the Tokyo office in six months.
You can also use in to say how long something takes:
- He finished the whole onboarding course in three days. (= it took him three days)
- We set up the new office in just two weeks.
Quick Self-Check
The project review is scheduled _____ 10 a.m. tomorrow.
Select your answer:
We need to submit the proposal _____ Friday afternoon.
Select your answer:
The company was founded _____ 2008.
Select your answer:
Don't worry — the technician will be there _____ about 20 minutes.
Select your answer:
We moved to the new office _____ last September.
Select your answer: