As anyone who has turned up for a midday meeting at midnight will tell you, clarity is vital when writing the time of day. But there are many ways to write the time, and the best approach isn’t always obvious. We have a few tips to help, though.
1. Words or Numerals?
You can write the time of day using either words or numerals. If you are using numerals, you would usually include both hours and minutes, although you can omit the minutes in less formal writing.
For instance, all the following would be acceptable:
She gets up at six in the morning every day.
She gets up at 6:00 in the morning every day.
She gets up at 6 o’clock in the morning every day.
As a rule, though, you would only write out the time as words when:
It is part of a full sentence, particularly in descriptive or literary writing.
You’re referring to an approximate or round time (e.g., saying “ten thirty” is fine, but you would not usually write “twenty-four minutes after eight”).
In most other cases, numerals are the clearer option for writing the time, especially in scientific and technical writing, where precision is vital.
2. AM and PM
The abbreviations AM and PM can be used when writing the time as numerals. Each applies to a different time of day:
AM is short for ante meridiem, meaning “before noon.”
PM is short for post meridiem, meaning “after noon.”
As such, we use AM and PM to indicate the time of day when we are using a 12-hour clock. We can see how this works more clearly if we write out various times of day in both 12-hour and 24-hour formats:
Three in the morning
Half past eight in the morning
Three in the afternoon
Half past eight in the evening
You can see here that we need AM and PM with the twelve-hour clock for clarity. Without them, we wouldn’t be able to tell the difference between, e.g., midday and midnight. Likewise, though, you do not need to include AM or PM with a 24-hour time because it is already clear.
There are also several ways to write AM and PM, including:
ALL CAPS, small caps, or lower case (e.g., 12 AM, 12 AM, or 12 am)
With or without periods between the letters (e.g., 8 PM or 8 P.M.)
With or without a space after the number (e.g., 1 AM or 1AM)
Consistency is key here, so make sure to apply one style throughout your document. You may also want to check your style guide if you have one, as some organizations will have their own rules for how to write AM and PM.
3. When to Use O’clock
You’ll have noticed we use “o’clock” in one of the examples above. This term means “of the clock,” so we can use it to show that a number refers to a time.
However, you should only use “o’clock” with exact hours:
It is precisely 5 o’clock.✔
I’m leaving at seven o’clock.✔
It arrived at 7:34 o’clock.✘
The gig starts at half past seven o’clock.✘
We’ll save a discussion of when wine o’clock is for another blog post.
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4. Past, After, Till, and To
When writing the time as words, use “after,” “past,” and “to” for intervals between hours. You can combine these terms with either numbers or the words “half” and “quarter” depending on the time in question:
Use after or past for intervals up to half an hour past the hour.
Use to for any interval after the half hour up to the hour.
Use half past to indicate 30 minutes past the hour.
Use quarter pastor quarter after for 15 minutes after the hour.
Use quarter to for 15 minutes up to the hour.
For example, we would use the above accordingly in the following times:
7:05 → Five after seven
7:15 → Quarter past seven
7:30 → Half past seven
7:45 → Quarter to eight
7:55 → Five to eight
Keep in mind that using “after” for times is only standard in American English. In other English dialects, “past” is far more common.
5. Punctuating the Time
When writing the time as numerals, you can use either a colon or a period between the hour and the minutes. In some cases, such as in the military, you can even write out a 24-hour time without any punctuation.
For instance, the following are all acceptable ways of punctuating a time:
We need to leave by 6:45 pm at the latest.✔
We need to leave by 6.45 pm at the latest.✔
We need to leave by 1845 at the latest.✔
The colon is the most common option here, but it is a matter of preference. Unless you’re in the military, in which case we suggest sticking to protocol.
6. Time Zones
For the contiguous states in the USA, we have four standard time zones:
Pacific Time (PT) [UTC-08:00]
Mountain Time (MT) [UTC-07:00]
Central Time (CT) [UTC-06:00]
Eastern Time (ET) [UTC-5:00]
We also have regional time zones for Alaska, Hawaii, and 5 US dependencies, plus daylight saving time in some places during the warmer months of the year. And people in other countries use different time zones entirely!
Basically, we’re saying geography can make time complicated.
This is why we sometimes include a time zone when writing the time. The initials UTC above, for instance, stand for Coordinated Universal Time. We can use this to compare times in different places. So, “UTC-8:00” means Pacific Time is 8 hours behind UTC. And since we know Pacific Time is 8 hours behind UTC and Eastern Time is 5 hours behind UTC, we can work out that ET is 3 hours ahead of PT.
In other words, by including a time zone when we write a time, we can help people in other places “translate” it into their own time zone.
This is important if you are writing for an international audience, since not everyone will be in the same time zone. You thus need to include a set of time zone initials so your reader can calculate the equivalent time where they are. For example, if we were writing a time for an international audience, we might say:
The live broadcast will begin at 9:00 pm UTC.
Someone in Bolivia could then look up the difference between UTC and BOT (Bolivia Time) and know the broadcast begins at 5:00 pm where they are.
7. Avoiding Redundancy when Writing the Time
In writing, redundancy means using a word unnecessarily. We mentioned above, for example, that you do not need to use AM or PM with 24-hour times because we already know whether a time is the morning or afternoon/evening when using a 24-hour clock.
Other cases of temporal redundancy you may want to avoid include:
Using “in the morning,” “in the afternoon,” etc., alongside AM/PM.
Combining “in the morning,” “in the afternoon,” etc., with a 24-hour time.
Using “midday,” “noon,” or “midnight” alongside a time in numbers.
We’ll end this post with a few examples of redundancies so you know what to watch out for. Check out the table below, good luck writing the time, and let us know if you need any help proofreading your work.
The event ends at 17:00 PM.
The event ends at 17:00.
The event ends at 5:00 PM.
We leave at 6AM in the morning.
We leave at 6AM.
We leave at 6:00 in the morning.
He went to bed at 23:00 at night.
He went to bed at 23:00.
He went to bed at 11:00 at night.
I’ll see you at twelve noon.
I’ll see you at twelve.
I’ll see you at noon.
(N.B. ‘Noon’ is the better correction here, since ‘twelve’ by itself could be either midday or midnight.)