In American English, write the date as month, day, year with cardinal numbers ("November 16, 2016"), and use ordinal numbers only when the day comes before the month ("the 16th of November"). For times, use numerals with a.m. or p.m. ("8:45 a.m."), and write "noon" and "midnight" as words.
You write dates and times all the time when you communicate with others. But what are the proper ways to write them? How exactly do you write a date in a sentence? What about a.m. and p.m.? And how do you spell out a date correctly?
These are some of the questions many people have about dates, times, and grammar rules. Some are also unsure when to use ordinal and cardinal numbers (both are explained below), and when it is right to add "st", "nd", "rd", or "th". This guide covers the rules for writing dates and times, along with a few tips and exceptions.
Ordinal vs. cardinal numbers
When you write dates and times, the question of ordinal and cardinal numbers always comes up. Cardinal numbers are the counting numbers: 0, 1, 2, 3, 4, and so on. Ordinal numbers show a position or rank: first, second, third, fourth (1st, 2nd, 3rd, 4th), and so on. (In mathematics, especially in set theory, the two terms have more technical meanings.)
Still, when people write the date January 1, chances are they write an ordinal number: January 1st. That is because people tend to write things the way they say or hear them, which is why many write "January 1st" or "December 25th", with the "st" after the 1 and the "th" after the 25. But you do not need ordinal numbers when you write these dates. There are only a few cases in which you should add the "st", "nd", "rd", or "th".
Here are some examples and rules to follow:
- We are meeting on November 16.
- We are meeting on the 16th of November.
- Some of the kids played tricks on everyone on April 1. (Many people would write "April 1st" here, because that is how they say it.)
- On the 1st of April, everyone likes to play April Fools' jokes.
Remember that you only need ordinal numbers in dates when the day comes before the month.
Examples:
- I wrote the article on the 16th of December.
- The 1st of April is a joker's holiday.
All-numeric dates
Be careful with dates written only in numbers. In the United States, 11/12/2016 means November 12, but in British English and in most other countries, it means 11 December. To avoid confusion, write the month as a word, or use the international format 2016-11-12 (year, month, day).
Writing the time of day
When it comes to the time of day, some writers prefer numerals, while others spell the time out.
Examples:
- He goes to work at 4 o'clock in the morning every day.
- She gets up at half past five to be extra early.
Writers who want to be more precise give the exact time in numerals.
Examples:
- Angela waited for her boyfriend's flight, which arrived at 8:45 a.m.
- I would really like everyone to be at the party at exactly 5:30 p.m. this Saturday.
There are several ways to write a.m. and p.m. The most common one in American English is lowercase with periods: a.m. and p.m. You will also see AM and PM, or am and pm, which is common in British English.
Some people put a space between the time and the abbreviation, while others do not. Most style guides use a space, but whichever form you choose, use it consistently.
Examples:
- She got there at exactly 9:22 p.m.
- She got there at exactly 9:22pm.
Writing decades
When you write a decade in numerals, keep these rules in mind. The plural s takes no apostrophe, and an apostrophe only replaces the missing digits of a shortened year.
Correct:
- Many people think that the music of the 1950s was the best ever.
- I like the music of the '50s, because it makes me feel nostalgic.
- During the 1950s, rock and roll took over the charts.
Incorrect:
- During the '50's, teen songs were the most popular.
- Many people think that the music of the 1950's was the best ever.
The rules for apostrophes explain why.
Commas and dates
No comma is needed between a month and a year.
Example:
- Paula and I met in September 2009.
But when you add the day, put a comma between the day and the year. If the sentence goes on after the year, put another comma after it.
Examples:
- Dolores and I saw a movie on July 6, 2016.
- On July 6, 2016, Dolores and I saw a movie.
When the day comes before the month, no comma is needed. This day, month, year order is standard in British English and in most other countries, and the US military uses it as well.
Example:
- The doctor released the results of the test on 24 May 2016.
Noon and midnight
One last thing: when you mean noon or midnight, it is better to use those words than to write 12:00 p.m. or 12:00 a.m. The words make it much clearer to the reader exactly what time you mean.
Dates and times are only one of the details that make a text look polished. For the others, see the rules for writing numbers and the guide to first, second, and third person point of view.