Prepositions of Time in English: IN, ON and AT with Examples and Exercises

If you have ever frozen mid-sentence wondering whether it is in Monday, on Monday or at Monday, relax, you are not the only one. Prepositions of time look like a minor detail, and yet they turn up in almost every sentence you want to say: when you are meeting someone, when you were born, what time the class starts or what you are doing at the weekend.

The confusion usually comes from your first language. Spanish, for example, covers almost all of this with a single word, «en» (en julio, en 2020, en verano), or with no preposition at all (el lunes, a las tres), whereas English shares the same meanings out between in, on and at. The good news is that there is a logic behind it, and once you see it, the vast majority of cases sort themselves out.

In this guide I will walk you through the pyramid rule, when to use each preposition, the cases where you use no preposition at all (there are more than you might think), the mistakes I correct in class every week, and four exercises to practise. Let’s get started!

What are prepositions of time?

They are the words we put in front of a time expression to place an action in time: at 7 o’clock, on Friday, in August. There are a few more (for, since, during, until…) and I will cover the essential ones at the end, but the three you will use every single day, and the three that cause the most mistakes, are in, on and at.

If you have just been through the verb to be, this is the natural next step: put the two together and you can say things like My birthday is in May or The class is at six without a second thought.

The pyramid rule: from general to specific

This is the trick I give in class, and it works wonderfully. Picture an upside-down pyramid: the widest part at the top, the most precise part at the bottom. The more specific the moment, the further down the pyramid you go, from in to on, and from on to at.

Preposition	What for	🇬🇧 Examples
IN	Long or less specific periods	in May, in 2019, in summer, in the 1990s
ON	Days and dates	on Monday, on 5 March, on my birthday
AT	Exact moments	at 8 o’clock, at midnight, at lunchtime

With this idea in your head you will get it right most of the time. What is left is a handful of exceptions and fixed expressions, which I explain below.

When to use IN

We use in with the longest or least specific periods of time:

• Months: in January, in August
• Years: in 2008, in 1492
• Seasons: in summer, in (the) winter
• Decades and centuries: in the 1980s, in the 21st century
• Parts of the day: in the morning, in the afternoon, in the evening
• Eras: in the past, in the future, in the Middle Ages

Some examples:

• We usually go to the beach in August.
• I always feel more creative in the morning.
• This house was built in the 19th century.

Notice the parts of the day: they break the pyramid logic, because a morning is hardly a «long» period, and yet it takes in. Learn them as a set: in the morning, in the afternoon, in the evening… but at night, which we will come to shortly.

A use of IN that people forget: «from now»

With an amount of time, in means «after that time, counting from now»: The film starts in ten minutes, I’ll be back in two weeks. Don’t mix it up with for, which expresses duration: I’ll be away for two weeks means you will be gone during those two weeks.

When to use ON

We use on with specific days:

• Days of the week: on Monday, on Saturday
• Dates: on 12 October, on the 3rd of May
• Special days: on my birthday, on Christmas Day, on New Year’s Eve
• Day + part of the day: on Monday morning, on Saturday night, on the evening of the 14th

Some examples:

• The museum is closed on Mondays.
• We’re having a party on my birthday.
• I’ll send you the report on Friday afternoon.

Two important details. First, to talk about something you do regularly on a particular day, make the day plural: I go swimming on Tuesdays. Second, watch out for the last point on the list, because it is where most mistakes happen: we say in the morning, but on Monday morning. As soon as a specific day appears, on takes over.

For dates, the usual British form is on the 3rd of May or, in writing, on 3 May. If you want to revise how dates are said and written, it is all in the post on the date in English, and the ordinals (first, second, third…) are in the one on numbers in English.

When to use AT

We use at with the most precise moments:

• Clock times: at 7 o’clock, at half past six, at 9.30
• Specific points in the day: at noon, at midnight, at lunchtime, at sunset
• Night in general: at night
• Holidays, as a period: at Christmas, at Easter
• The weekend (in British English): at the weekend
• Fixed expressions: at the moment, at the same time, at the beginning, at the end

Some examples:

• My flight leaves at 6.15 in the morning.
• The streets are very quiet at night.
• I’m really busy at the moment.

If telling the time in English still takes you a moment, have a look at the post on telling the time in English before you carry on, because at almost always comes with one.

When NOT to use a preposition

This is the section that will save you the most mistakes. Before next, last, this and every, and with today, tomorrow, yesterday and tonight, you use no preposition at all.

❌ Incorrect	✅ Correct
See you on next Monday.	See you next Monday.
We met in last summer.	We met last summer.
What are you doing at this weekend?	What are you doing this weekend?
I go running on every Friday.	I go running every Friday.
The exam is on tomorrow.	The exam is tomorrow.
I saw her in yesterday morning.	I saw her yesterday morning.

The same goes for ago, which comes after the amount of time and takes no preposition: I started learning English three years ago.

The cases that cause the most doubts

With the pyramid and the list above you have almost everything covered, but a few pairs deserve a warning of their own.

In the morning, but on Monday morning

We have seen it already, but it is so common that it bears repeating: a part of the day on its own takes in; put a specific day in front of it and it switches to on. I study in the morning, but I have an exam on Thursday morning.

At night and in the night

At night means during the night in general: I can’t sleep at night. In the night is used for something that happened during one particular night: I woke up twice in the night. If in doubt, at night is the safe option.

At Christmas and on Christmas Day

At Christmas refers to the festive period as a whole: We always visit my grandparents at Christmas. On Christmas Day is the 25th itself, and since it is a day, it takes on. The same applies to at Easter and on Easter Sunday.

At the weekend and on the weekend

No mistake possible here: both are correct. At the weekend is the usual form in British English and on the weekend in American English. Pick one and stick to it.

On time and in time

On time means punctual, at the planned time: The train left on time. In time means early enough, with enough time for something: We got to the cinema just in time for the film.

At the end and in the end

At the end (of) is the final point of something: at the end of the film, at the end of the month. In the end means «finally», after thinking about it or after a process: In the end, we decided to stay at home.

Common mistakes with prepositions of time

These are the mistakes I correct over and over again, especially with Spanish speakers. Avoid them and your English will sound noticeably more natural straight away.

❌ Incorrect	✅ Correct	Why
I was born on 1995.	I was born in 1995.	Years take in.
The class starts in 9.	The class starts at 9.	Clock times take at.
I go to the gym in Mondays.	I go to the gym on Mondays.	Days take on.
I’ll call you in Monday morning.	I’ll call you on Monday morning.	A specific day means on.
See you on next week.	See you next week.	Next, last, this and every take no preposition.
I don’t like driving in the night.	I don’t like driving at night.	Night in general is at night.
We met in Christmas Day.	We met on Christmas Day.	It is a specific day, so it takes on.
I’ll finish it in the end of the week.	I’ll finish it at the end of the week.	The final point of something is at the end of.

Other prepositions of time worth knowing

In, on and at are the stars of the show, but as soon as you start building longer sentences you will come across these as well:

• for: duration, a length of time. I lived in London for three years.
• since: the starting point. I’ve worked here since 2020.
• during: within a period or an event. My phone rang during the film.
• until (or till): up to a point in time. The shop is open until 8 p.m.
• by: at the latest, a deadline. Please send it by Friday.
• from… to (or until): the start and the end. I work from 9 to 5.

For and since go hand in hand with the Present Perfect Simple, and if you are unsure whether to use for or during, I have a whole post on the difference between FOR and DURING.

Prepositions of time in the Cambridge exams

They may be small, but in the Cambridge exams they win (and lose) more marks than you would expect:

• A2 Key and B1 Preliminary, Writing. The email task almost always asks you to suggest a plan or arrange to meet someone: Let’s meet at 6 on Saturday. An in Saturday is exactly the kind of slip the examiner notes under the Language criterion.
• A2 Key and B1 Preliminary, Speaking. The first part asks about your routine and your plans: What do you do at the weekend?, When is your birthday? Answering with the right preposition, without hesitating, is basic grammatical control.
• Gap-fill tasks (open cloze). In the A2 and B1 Reading papers, and in Use of English Part 2 of B2 First, prepositions make perfect candidates for a gap, and fixed expressions such as at the end, in the end, on time and in time come up again and again.

And speaking of routines, the post on daily routines vocabulary is a great way to practise in the morning, at night and on Mondays in context.

Prepositions of time summary table

	Use it with	🇬🇧 Examples
IN	Months, years, seasons, decades, centuries, parts of the day and «from now»	in May, in 2020, in winter, in the morning, in ten minutes
ON	Days, dates, special days and day + part of the day	on Monday, on 5 March, on my birthday, on Friday night
AT	Clock times, specific moments, holidays, night and the weekend (UK)	at 6 o’clock, at midnight, at night, at Christmas, at the weekend
No preposition	next, last, this, every, today, tomorrow, yesterday, tonight	next week, last year, every day, tomorrow morning

Prepositions of time exercises

You have the theory, so now it is time to practise. Here are four exercises, from the simplest to the most complete, each with its answers. Good luck!

And if you prefer a version in text that you can copy and paste, you have it down here 👇

Exercise 1: in, on or at?

Choose the correct preposition: in, on or at.

Exercise 2: complete the sentences

Complete the sentences with in, on or at.

Exercise 3: preposition or no preposition?

Choose the correct option. Sometimes no preposition is needed.

Exercise 4: spot the mistake

Decide whether each sentence is Correct or Incorrect. If it is Incorrect, write the full correct sentence.

Frequently asked questions about prepositions of time

When do you use in, on and at?

In for long periods (months, years, seasons, parts of the day), on for days and dates, and at for exact moments such as clock times. From general to specific.

Is it at the weekend or on the weekend?

Both are correct. At the weekend is the usual form in British English and on the weekend in American English.

Why is it in the morning but at night?

Because it is a fixed expression rather than a logical rule. Learn them as a set: in the morning, in the afternoon, in the evening and at night.

Do next week or last Monday take a preposition?

No. There is no preposition before next, last, this and every, nor with today, tomorrow, yesterday or tonight.

What is the difference between on time and in time?

On time means punctual, at the planned time. In time means early enough, with enough time for something.

Conclusion

Prepositions of time look like a minor detail, but they really stand out when they go wrong. If you take three ideas away from this post, make them these: the pyramid (in for the general, on for days and dates, at for exact moments), no preposition before next, last, this and every, and on as soon as a specific day appears, even when morning or night comes with it.

Now it is your turn: do the exercises above and, if you get one wrong, go back to the summary table and work out which part of the pyramid it slipped through. That is the fastest way to make it stick for good.

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See you in the next post. Until then, don’t forget to keep smiling! 🙂