Prepositions of Time
Prepositions of time tell us when something happens. The three most important are at, on, and in — each used for different units of time.
At, on, and in — the core three
The single most important thing to learn about prepositions of time is when to use at, on, and in. A simple rule of thumb: the more specific the time, the smaller the preposition.
- at 6 o'clock
- at noon / midnight
- at sunrise / sunset
- at the weekend (BrE)
- at Christmas / Easter
- at the moment
- on Monday
- on 5th July
- on New Year's Day
- on my birthday
- on a weekday
- on the weekend (AmE)
- in July / in summer
- in 2024
- in the morning
- in the 20th century
- in the past / future
- in three days' time
The meeting starts at 9 a.m. on Monday in January.
She was born at midnight on a Thursday in 1995.
I'll see you at Christmas — we arrive on the 24th.
Other important prepositions of time
| Preposition | Use | Example |
|---|---|---|
| for | Duration of time | She waited for two hours. I've lived here for years. |
| since | Starting point up to now | He has lived here since 2015. I've known her since school. |
| during | Within a period | It rained during the match. She slept during the film. |
| by | No later than a deadline | Please finish by Friday. She will arrive by noon. |
| until / till | Up to a point in time | I worked until midnight. The shop is open till 9. |
| before | Earlier than | Call me before 6 o'clock. Finish before lunch. |
| after | Later than | Let's meet after dinner. She called after midnight. |
| within | Inside a time limit | Reply within 24 hours. I'll be there within an hour. |
| from … to | A span of time | The shop is open from 9 to 5. |
For vs. since — a key distinction
These two are frequently confused. Both relate to duration with the present perfect, but they work differently.
- for + duration (how long): for two years, for a week, for ages, for a long time
- since + starting point (when it began): since Monday, since 2010, since she was a child
I have lived here for ten years. (duration — how long)
I have lived here since 2014. (starting point — when it began)
She has been waiting for two hours. / since two o'clock.
No preposition with certain time expressions
Do not use at, on, or in before: last, next, this, every, yesterday, today, tomorrow.
I saw her last Monday. (not: on last Monday)
We are meeting next Friday. (not: on next Friday)
He called yesterday. (not: on yesterday)
She comes every day. (not: on every day)
By vs. until: By means no later than a deadline — the action should be completed before that point: Finish by Friday. Until means continuously up to that point: I worked until Friday. They are not interchangeable.
Memory tip — AT IN ON: Think of a target: at hits an exact point (a bullseye — precise time), on lands on a surface (a day — flat like a calendar page), in goes inside a container (a month, year, or season — a longer period that contains the event).