Elementary English
For an easy-to-study reference chart, scroll to the bottom of the page.
Quick Reference
Use "at" with precise times (at 3 o'clock, at midnight, at the moment, etc.)
Use "on" with days and dates (on Monday, on January 14th, etc.)
Use "in" with months, years, decades, centuries, historical periods, and longer periods of time (in January, in 1999, in the 1950s, in the Middle Ages, etc.)
Use "in" for most times of day (in the morning, in the afternoon, in the evening).
Use "at" for "at night." "In the night" is also used, however, but mostly in literature and poetry.
Use "on" for days of the week combined with a time of day (on Friday morning, on Thursday afternoon, on Sunday evening, on Tuesday night)
People in North America typically use "on the weekend." People in the British Isles typically use "at the weekend."
Mastering the three major English prepositions of time—at, on, and in—is essential for accurate communication. If you want to organize a meeting, invite someone for dinner, tell someone your date of birth, you'll need to use prepositions. In this article, we'll learn how to use at, on, and in effectively.
To begin, test yourself. Which preposition should you use in these five cases?
"I'll see you _____ Wednesday."
"The meeting started _____ 9 o'clock."
"I was born _____ April."
"Halloween is _____ October 31st."
"She was born _____ 2015."
We'll come back to these in a little bit. For now, let's continue learning.
So, are there any general rules for at, on, and in? Luckily, yes! However, please note that I am stressing the phrase general rules. So...
In general, at is used for exact times, on is used for individual days, and in is used for longer periods of time. To explain most cases, you can think of it as a pyramid which becomes more precise as you move closer to the point at the top.
So, what does this mean? Let's look at things one at a time.
At
Use at with exact times. This means the hours on a clock. Let's look at some examples:
"I'll see you at 3 o'clock."
"The meeting ended at 10:30."
"We had lunch at noon."
"I fell asleep at midnight."
Okay, so far, so good, right? But there are other cases and common phrases which don't explicitly refer to a specific time on a clock. Here are some examples:
at the moment
at the time
at this/that time
at sunrise
at sunset
at lunch
at dinnertime
at bedtime
at the same time
at night
at Christmas
*at the weekend
For the first nine cases, we can still say that the times are precise. "At the moment" means "right now," or "at this exact time." "At the time" means "during the precise moment or period we are discussing." "At sunrise" and "At sunset" both refer to the precise times that sunrise happens in the morning, and sunset happens in the evening. You can use a search engine right now to learn the precise time that the sun will rise in Sydney, Australia tomorrow, for instance. Lunch, dinnertime, and bedtime are also fairly specific events which happen at a particular time. Finally, "at the same time" means "simultaneously," or "more than one action or event happening at exactly the same time or moment." All of these fit with the idea of at being used for exact (or nearly exact) times.
However, "at night" is an irregularity. I suppose we can think of night as a period when most people are asleep, and in that way, we can try to make it feel logical that nighttime is an exact time when many people are doing the same thing, but we really know it's not the same as saying "at 5 o'clock," for example.
"At Christmas" is even weirder because we don't necessarily mean Christmas Day. In fact, at is often used to refer to multi-day holidays. It's close in meaning to during in this way. So, you can say "I'll see you at Christmastime," which means "I'll see you on one of the days of Christmas." If you want to mention a specific day that happens during Christmas--specifically Christmas Eve or Christmas Day--you need to say "I'll see you on Christmas Day" or "We saw each other on Christmas Eve." Fortunately, this isn't a situation that you need to worry about too often, and I'll describe the on part shortly.
Before I do that, I need to address "at the weekend," which is typically used to discuss the weekend in England and its surrounding English-speaking areas (or "in British English," if you prefer). In North America, "on the weekend" is what is preferred by the vast majority of speakers. As with many languages, phrases and linguistic preferences can change depending on the region.
Since we've been talking about on a little bit in the last two paragraphs, let's take a detailed look at it.
On
On is used with individual days. This means days and dates. Essentially, if you can point to a day on a calendar, you can use on to talk about that day. Pay attention to the following examples:
"I'll see you on Saturday."
"She was born on August 10th, 2001."
"Are you going to be busy on Valentine's Day?"
"We're going to a party on the 4th of July."
"My birthday is on June 11th."
Some people have problems with on because while they know it is used with days and dates, they don't know that it is also used for single-day holidays. Remember: If you can point to a single day on a calendar, use on.
As we have already discussed above, you can also use on to mention what you did during or on the weekend in North America.
Finally, if you want to mention what you did during a specific part of the day on a specific day of the week, use on. Here is what I mean:
"We saw each other on Tuesday morning."
"He's going to meet me on Saturday afternoon."
"Are you free on Thursday evening?"
"I didn't do anything on Friday night."
Not bad, right? Just make sure you don't say "at Friday night" just because you know that you're supposed to say "at night." The day of the week is the most important part of time phrases like "Friday night," and as we know, days of the week need on, which means it should be "on Friday night."
Wow. This section was much easier than the at section, wasn't it? There's only one more preposition to go, and then we can review those 5 questions you did at the start of the page...
In
In is used with longer periods of time. This means months, years, decades (10 years), centuries (100 years), millennia (1000 years), historical periods, and seasons. Basically, if the period is one month or more, use in. Are you ready for some examples? Here we go:
"I graduated in September."
"My family moved to Ireland in 2016."
"Grunge music was really popular in the 1990s."
"World War 2 happened in the 20th century." / "...in the 1900s."
"Do you think we'll master space travel in this millennium?"
"Would you want to live in the Middle Ages?"
"The best time to buy a new barbecue is in the fall." (Bonus note: Seasons can be written with or without the article "the." You can say "in the fall" or "in fall." It's your call.)
To practice using in with years, answer this question: In what year were you born? (Answer: "I was born in _____.") Remember, if you mention the date on which you were born, you must use on instead. To illustrate this, you can say "I was born in 1995," or "I was born on July 10th, 1995."
You can also use in to talk about specific times of day. Namely:
in the morning
in the afternoon
in the evening
While you can say "in the night," at night is what is typically used. Here are some examples of in with times of day.
"Can we talk about this in the morning?"
"I'll see you in the afternoon."
"Do you usually stay at home in the evening?"
"I've been having a hard time falling asleep at night."
Finally, you can use in to talk about the length of time that will pass before something happens in the future. For instance, you can say "I'll see you in 30 minutes," or "My father is going to visit us in 3 days." You can even say "He's going to graduate in 2 years."
And these are all the most important points about how to use at, on, and in. How do you feel? Are you ready to test your knowledge? Let's go back to the 5 questions at the top of this page. Answer them then check the answers directly under them.
"I'll see you _____ Wednesday."
"The meeting started _____ 9 o'clock."
"I was born _____ April."
"Halloween is _____ October 31st."
"She was born _____ 2015."
Answers: I'll see you on Wednesday. / The meeting started at 9 o'clock. / I was born in April. / Halloween is on October 31st. / She was born in 2015.
One more thing...
So, you now have a better understanding of how to use at, on, and in. This is good news! However, as you probably know, there are more ways to talk about time.
For instance, if you don't want to give a precise time for something, you can use around or about instead of at. Around and about mean approximately in these cases. For instance, "I should be there around 5 o'clock," or "What time is it?" "I don't know. It must be about 2 o'clock or something."
Next, if you want to talk about the duration of time which something takes, use for. For example, "I worked there for 6 years," or "We waited for 45 minutes."
Finally, you can use since to talk about specific periods in the past. For instance, "We haven't seen each other since high school," or "I haven't seen that movie since I was 12 years old."
And that's it! I hope you feel better informed about when to use at, on, and in, so you can start planning your next party, work meeting, or dinner reservation with confidence.
Prepositions Chart
At | On | In |
Hours at 6 o'clock at 5:15 at noon at midnight | Days on Monday on Tuesday on Friday on Sunday | Years in 1995 in 2015 in 1789 in 2001 |
Precise times / events at the moment ("now") at sunrise at sunset at lunch at dinnertime at bedtime at the start of the day at the end of the day | Dates on July 14th on February 23rd, 1998 on the 19th of August on March 19th | Decades in the 1990s in the 1970s in the 2010s in the 1850s |
"Time" expressions at the time at this/that time | Holidays / Individual days on a calendar on my birthday on Valentine's Day on Christmas Day on New Year's Eve | Centuries in the 1900s in the 20th century in the 1800s in the 19th century |
Other at night at the weekend (British English) | Days with times of day on Tuesday morning on Wednesday afternoon on Thursday evening on Saturday night | Historical periods in the Middle Ages in the Victorian era in the Renaissance in the early modern period |
| Other on the weekend (North American English) | Seasons in (the) spring in (the) summer in (the) fall in (the) winter |
| | Times of day in the morning in the afternoon in the evening *in the night (Possible, especially in literature and poetry, but "at night" is much more common in everyday English.) |
| | Length of time before a future event in 2 hours in 30 minutes in a year |
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