Prepositions of Time: Uses, Rules and Examples

Overview

Prepositions of time are words that explain when something happens, for how long, or in relation to what point in time. They are among the most frequently used prepositions in English, and getting them right makes a significant difference to how clearly a speaker or writer communicates.

At the centre of prepositions of time are three familiar words: in, on, and at. Each one attaches to a different type of time expression, and understanding which one to use with which type is a skill worth developing early. Beyond these three, a second group of prepositions, including by, until, since, for, during, from, and after, adds precision about duration, limits, and sequences.

In, On, and At for Time

The three core prepositions of time each apply to a different scale of time expression. A practical way to remember them is to move from large to small: in covers the largest time units, on covers specific days and dates, and at covers precise clock times and fixed moments.

In

In is used with years, decades, centuries, months, seasons, and parts of the day.

One exception worth noting: in the morning, in the afternoon, and in the evening all use in, but at night does not. Night takes at, not in.

On

On is used with specific days of the week, full calendar dates, and named holidays that are treated as single days.

On can also combine with a day and a part of that day, as in on Monday morning or on Friday afternoon. In these combinations, on takes precedence over in.

At

At is used with clock times, mealtimes, and a small number of fixed time expressions.

Fixed expressions that take at include at the moment, at the same time, at present, at the weekend (British English), and at Christmas or at Easter when referring to the general period rather than the specific day.

By, Until, and Before

These three prepositions all relate to a deadline or an endpoint, but they work differently from one another.

By means no later than a specific time. The action must be completed before or at that point.

Until (or till in informal use) means up to a point in time and not beyond it. It describes how long a situation continues.

Before means earlier than a point in time, without implying a deadline or a continuous state.

The clearest distinction between by and until is this: by focuses on a completed action at a deadline, while until describes a state or activity that continues up to a point and then stops.

Since and For

Both since and for describe duration, but they approach it differently. Since names the starting point of a period. For gives the length of the period itself.

Since answers: from when? For answers: how long?

Since is used with a specific point in time: a year, a date, a named event, or a moment.

For is used with a length of time: a number of minutes, hours, days, weeks, months, or years.

During, From, and After

During explains that something happens within a specific period of time. It does not say when within that period; it only states that the event falls inside it.

From marks the starting point of a period and is often paired with to or until to show where the period ends.

After means following a particular time or event. It is the direct opposite of before.

Comparing Prepositions of Time

Common Mistakes to Avoid

Mistake 1: Using In Instead of At for Clock Times

Clock times always take at, never in. This is one of the most common errors at A2 level.

Mistake 2: Using On Instead of In for Months and Years

Months and years take in, not on. The confusion arises because dates (day and month together) use on.

Mistake 3: Confusing Since and For

Since names a starting point. For gives a duration. Using one where the other belongs produces an incorrect sentence.

Mistake 4: Confusing By and Until

By is for deadlines attached to a completed action. Until is for the endpoint of an ongoing situation. Swapping them produces a sentence that is grammatically odd or logically unclear.

Mistake 5: Using During Instead of For

During specifies a named period; it does not state a length of time. For lengths of time, for is required.

Mistake 6: Omitting At in Fixed Expressions

Expressions like at the moment, at the weekend, and at night are fixed. Dropping at or replacing it with another preposition changes the phrase or makes it ungrammatical.

Practice Exercises

Exercise 1: Choose the Correct Preposition

Choose the correct preposition to complete each sentence.

1. The presentation starts _______ half past two. (in / on / at)
2. She was born _______ the ninth of October. (in / on / at)
3. He has been a teacher _______ fifteen years. (since / for)
4. The café is open _______ seven in the morning _______ ten at night. (from / to)
5. Please hand in your assignment _______ next Thursday. (by / until)
6. It is usually cold here _______ January. (in / on / at)
7. They talked _______ dinner but did not argue. (during / for)

Exercise 2: Since or For

Complete each sentence with since or for.

1. She has not spoken to him _______ their argument last month.
2. The children have been awake _______ six o'clock this morning.
3. He lived in that city _______ almost a decade.
4. I have been waiting _______ over an hour.
5. The museum has been closed _______ the renovation began.

Exercise 3: Correct the Error

Find and correct the one preposition error in each sentence.

1. The meeting begins in nine o'clock sharp.
2. His birthday is in the third of August.
3. She has worked at this company since ten years.
4. Several people left the hall during two hours of delays.
5. He felt tired for the whole journey because it was a long drive.

Exercise 4: Complete With the Correct Preposition

Fill in each blank with in, on, at, by, until, since, or for.

1. The office closes _______ six, so please arrive _______ five thirty.
2. She has lived here _______ she finished university.
3. The event takes place _______ Saturday morning.
4. He read the report _______ twenty minutes.
5. We need the signed document _______ end of business today.
6. The factory was built _______ the nineteenth century.

Summary

Most errors with prepositions of time come from a small number of predictable confusions. Keeping the large-to-small pattern for in, on, and at in mind, and maintaining the distinction between starting point and duration for since and for, will resolve the majority of mistakes at this level.