Prepositions of time
A1 16 / 50
In short
We use at for clock times, on for days and dates, and in for longer periods (months, seasons, years, parts of the day). With words like today, tomorrow, yesterday and this / next / last + time, we use no preposition at all.
The rule
The three main time prepositions get smaller from in to at:
| Preposition | Use it for | Examples |
|---|---|---|
| at | clock times, festivals, night, (BrE) the weekend | at 6 o’clock, at noon, at Christmas, at night, at the weekend |
| on | days and dates, named mornings/afternoons | on Monday, on 5 May, on my birthday, on weekdays, on Monday morning |
| in | months, seasons, years, centuries, parts of the day | in July, in summer, in 2024, in the 21st century, in the morning |
A simple memory hook: in = a long box (year, month, part of day) -> on = a day on the calendar -> at = an exact point (a clock time).
No preposition
Do not put a preposition before these time words:
| Word group | Right | Wrong |
|---|---|---|
| today, tomorrow, yesterday | I’ll call you tomorrow. | |
| this / next / last + time | I saw her last week. | |
| every + time | We meet every Monday. |
Other useful time words
| Word | Meaning | Example |
|---|---|---|
| for | how long (a duration) | for two hours, for three days |
| since | the starting point of something | since 2010, since Monday |
| during | inside a period / event | during the lesson, during the summer |
| from … to / until / till | start point to end point | from 9 to 5, from Monday until Friday |
| by | not later than (a deadline) | by 6 o’clock, by Friday |
| ago | a time back from now (goes after) | two days ago, a week ago |
Forms & patterns
A handy contrast: in the for parts of the day, but on when you name the day.
| Part of day alone | With a named day |
|---|---|
| in the morning | on Monday morning |
| in the afternoon | on Friday afternoon |
| in the evening | on Saturday evening |
| but: at night | on Sunday night |
for vs since (full work in lesson 25):
| Word | Answers | Example |
|---|---|---|
| for + length of time | ”How long?” | I have lived here for five years. |
| since + a point in time | ”Since when?” | I have lived here since 2019. |
ago comes after the time, with a past verb: I met him three years ago.
Examples
| English | Note |
|---|---|
| The film starts at 8 o’clock. | at + exact clock time. |
| We visit family at Christmas. | at + a festival. |
| I read a little at night. | Fixed phrase: at night. |
| My exam is on Monday. | on + a day of the week. |
| She was born on 12 March. | on + a date. |
| It often rains in April. | in + a month. |
| We moved here in 2021. | in + a year. |
| I get up early on Monday morning. | Named day -> on, not in the morning. |
| I’ll be ready by seven. | by = not later than seven. |
| They talked for an hour. | for + a duration. |
Common mistakes
- in Monday -> on Monday - days take on, not in.
- on the morning -> in the morning - parts of the day take in (but on Monday morning).
- at July -> in July - months take in.
- in last week -> last week - no preposition with this / next / last.
- since two hours -> for two hours - for = a length of time; since = a start point.
- He left before two hours -> He left two hours ago - use ago for time counted back from now.
Tips
- Shrinking sizes: in (months, years, seasons) > on (single days, dates) > at (exact times). The smaller the time, the smaller the word.
- Learn these as fixed chunks: at night, in the morning / afternoon / evening, at the weekend (BrE) / on the weekend (AmE).
- The moment a day name appears, switch to on: in the evening but on Tuesday evening.
- for answers how long? and since answers since when? - they pair naturally with the present perfect (lesson 25).