Part 1 — Prepositions of Time

At, on and in

At — an exact time or point

at 5 o’clock

at noon

at midnight

at night

at the weekend

Example

The meeting begins at 10 a.m.

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On — a day or date

on Monday

on 14 August

on my birthday

on Monday morning

Example

The office will reopen on Monday.

Use on when a day and part of day appear together:

on Friday evening

Compare:

in the evening

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In — a longer period

in June

in 2027

in winter

in the morning

in the twentieth century

Example

The examination will be held in September.

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At, on and in memory

🧠

At = exact point

On = day/date

In = longer period

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Since and for

Since — starting point

since Monday

since 2020

since morning

since I arrived

Example

She has lived here since 2020.

For — length of time

for two hours

for three years

for a long time

Example

She has lived here for three years.

Error

She has lived here since three years. ❌

She has lived here for three years. ✅

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By and until/till

By — deadline

An action happens no later than the stated time.

Submit the form by Friday.

The form may be submitted before Friday.

Until/till — continuation

An action or state continues up to the stated time.

Wait until Friday.

The waiting continues.

Contrast

Finish the work by 5 p.m.

Stay here until 5 p.m.

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During and while

During + noun

during the meeting

during the holidays

during the night

Example

He slept during the lecture.

While + clause

while the teacher was speaking

while I was studying

Example

He slept while the teacher was speaking.

Error

during I was studying ❌

while I was studying ✅

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From and to/until

The office is open from 9 to 5.

He worked from Monday until Friday.

Use from for the starting point.

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Within

Within means before the end of a period.

Reply within seven days.

This means any time before seven days have passed.

Compare:

Reply in seven days.

This often means after seven days.

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In and after with future time

In

I will return in two hours.

Two hours from now.

After

I returned after two hours.

Two hours passed before the past action.

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Before, after and ago

before the meeting

after lunch

two years ago

Example

She arrived before noon.

He left after dinner.

Ago is measured backward from now:

He arrived two days ago.

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On time and in time

On time — punctual

The train arrived on time.

It arrived at the scheduled time.

In time — early enough

We reached the station in time to catch the train.

We were not too late.

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At the end and in the end

At the end — final point of something

There is an exercise at the end of the chapter.

In the end — finally

In the end, they accepted the proposal.

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Fixed time expressions without a preposition

last week

next month

this morning

every day

yesterday

tomorrow

Incorrect

in last week ❌

on next Monday ❌ in ordinary use

Correct

last week

next Monday

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Time revision table