How to Write Dates in American English (With Examples)

In American English, dates go month first: October 16, 2026, or 10/16/2026 in numbers. Put a comma between the day and the year, and another comma after the year when the date falls in the middle of a sentence. In formal writing, use “October 16,” not “October 16th.”

That month-day-year order is the biggest difference from British and most international usage, which puts the day first. It’s also why a numeric date like 04/05/2026 can mean two different days depending on who reads it.

This GrammarVista.com USA guide covers every common format: written dates, numeric dates, ISO dates, days of the week, decades, and times, with a US vs UK comparison table.

The American Date Format: Month, Day, Year

The standard written American date names the month, then the day as a number, then the year.

• October 16, 2026
• July 4, 1776
• March 1, 2027

Americans say these dates with an ordinal (“October sixteenth”), but they write them with a plain number. That gap between speech and writing is why “October 16th” shows up so often in casual text.

Commas in full dates

A comma always separates the day from the year. When the full date sits inside a sentence, a second comma follows the year.

• Correct: On October 16, 2026, the office will close early.
• Incorrect: On October 16, 2026 the office will close early.

Think of the year as a parenthetical detail: it needs a comma on both sides. The same logic applies to “Austin, Texas, is hot,” which our guide to American punctuation rules explains alongside other comma basics.

Quick rule: Month and day plus year? Commas around the year. Month and year only? No comma at all.

Month and year only

When you leave out the day, drop the comma: October 2026 was a busy month. The same goes for a month and day without a year: The deadline is October 16.

Ordinals: October 16 or October 16th?

In formal and professional writing, use the cardinal number: October 16. Both the AP Stylebook and the Chicago Manual of Style call for “October 16,” not “October 16th,” when the month comes before the day.

Ordinals are fine in a few situations:

• When the day stands alone: The party is on the 16th.
• When the day comes before the month in a phrase: the 16th of October (less common in American writing).
• In informal messages, invitations, and holiday names: the Fourth of July.

Abbreviating months

AP style abbreviates longer month names when they appear with a specific date (Oct. 16, 2026) but spells out March, April, May, June, and July. Chicago generally spells out months in running text. If you’re unsure, spell the month out; it’s never wrong.

Numeric Dates and Why 04/05 Is Ambiguous

The American numeric format is MM/DD/YYYY: 10/16/2026. Forms, checks, and many US software settings use it.

The problem is that most of the world, including the UK, uses DD/MM/YYYY. To an American, 04/05/2026 is April 5. To a British reader, it’s 4 May. Nothing in the numbers tells you which system the writer used.

Some dates are safe by accident. 10/16/2026 can only be October 16, because there’s no 16th month. But any date where the day is 12 or lower can be misread.

Quick rule: If anyone outside the US will read it, spell out the month. “April 5, 2026” can’t be misread.

ISO 8601: the unambiguous option

For data, file names, and international documents, the international standard ISO 8601 writes dates largest unit first: 2026-10-16 (YYYY-MM-DD). The W3C’s note on date and time formats, a profile of ISO 8601, shows this “complete date” form with examples.

ISO dates read the same in every country and sort chronologically, which makes them ideal for file names like report-2026-10-16.pdf. Archival standards such as the Library of Congress Extended Date/Time Format build on the same structure.

US vs UK Date Formats Compared

Here’s how the two systems line up, with the ISO form for reference.

Notice that the British day-first style needs no comma between the day and the year. Dates are just one item on the list; our guide to American vs. British English differences covers spelling, vocabulary, and grammar too, and the US vs UK English section collects related posts.

Days of the Week

When you include the weekday, it comes first and takes a comma after it. The year still gets commas on both sides mid-sentence.

• The launch is on Friday, October 16, 2026, at noon.
• We’ll meet Friday, October 16.

Always capitalize days and months, and double-check that the weekday matches the date; it’s one of the simplest proofreading checks we recommend at GrammarVista.com USA.

Decades

Write decades with a plain s and no apostrophe: the 1990s, the 2020s.

• Correct: in the 1990s
• Incorrect: in the 1990’s
• Short form: the ’90s, with the apostrophe standing in for the missing digits
• Spelled out: the nineties, common in casual and literary writing

Writing Times the American Way

Americans mostly use the 12-hour clock with a.m. and p.m., written lowercase with periods in AP and Chicago style.

• The meeting starts at 9:30 a.m.
• Doors open at 7 p.m. (AP drops “:00” on the hour.)
• Use noon and midnight instead of 12 p.m. and 12 a.m., which many readers mix up.

Avoid redundancy like “9 a.m. in the morning” or “12 noon.” The 24-hour clock (14:30) is mostly used in the military, hospitals, and technical fields in the US.

Scheduling over text often skips formal rules entirely. If a coworker writes “EOD” or “OOO,” our guide to text slang meanings decodes it, and our post on text slang at work explains when shorthand is appropriate.

The Bottom Line

American dates follow one pattern: month, day, year, with commas around the year. Spell out the month for international readers, and use ISO 8601 when a date must be unambiguous.

For more style tips like these, explore the Punctuation section or start at GrammarVista.com USA, your guide to everyday American English.