Grammar Tip: Don’t Use Ordinal Numbers When Writing Dates

This is one of those quirky grammar rules that can be confounding because the rule for speaking differs from the rule for writing.

Ordinal numbers show order, or a position in a series: first (1^st), second (2^nd), third (3^rd), and so on. Cardinal numbers show an amount: one (1), two (2), three (3), and so on.

Except when it comes to dates.

When we are speaking and say a date, we usually use ordinal numbers. But when we write a date, we should use cardinal numbers.

This means when you orally invite someone to your party, you might say, “We’re having some people over for dinner on October tenth. Can you join us?”

But if you sent a written invitation, it would be, “We’re having some people over for dinner on October 10. Can you join us?”

Of course, if you sent that written invitation to someone and included a “bring a plus-one” note, that person would read, “October 10” but say to their plus-one, “I’ve been invited to a dinner party on October tenth. Would you like to go with me?”

Naturally, there are exceptions (aren't there always?). The exception to the written rule is when you're spelling out the number and put the day ahead of the month. It would be “the fifth of May” not “the five of May.”

Don’t you just love the English language?

Examples of how and how not to write dates:

Correct:

You’re invited to John’s birthday party on February 10, 2025.
The accident happened on August 31, 2024.
She had the baby on the twenty-fifth of December.
Mary Kay Ash was born May 12, 1918, and died November 22, 2001.

Incorrect:

You’re invited to John’s birthday party on February 10th, 2025.
The accident happened on August 31st, 2024.
She had the baby on the 25th of December.
Mary Kay Ash was born May 12th, 1918, and died November 22th, 2001.

Why are dates said and written this way in English? For the same reason that clip means to cut apart and attach together. For the same reason that a bat is an animal and a piece of sports equipment. For the same reason that the plural of kid is kids but the plural of child is children. It’s just English.