When I’m writing something that has dates included in it, how do I know when to use 1st or 5th when listing a date instead of just writing the number by itself? What is this called, anyways?

When to use cardinals and when to use ordinals

The short answer
When you’re writing dates in any context, you don’t need to include the st or the th (or the nd!). 

The details
Although we read and speak dates as ordinal numbers, we write them as cardinal numbers. (More on that below!) Write a date like this: June 5, 2021. Avoid writing “June 5th, 2021.”

Getting it right when writing dates

You may think that cardinals and ordinals have something to do with sports teams, but here we’re talking about numbers. Mixing up cardinal and ordinal numbers is a common mistake when writing dates.

Cardinal numbers indicate an amount—how many of something we have: one, two, three, four, five.

Ordinal numbers indicate position in a series: first, second, third, fourth, fifth.

Much more important than knowing the names of these numbers, however, is knowing how to use them, especially with dates.

Using cardinals when writing dates

Dates are tricky because we say “November fifteenth,” “May tenth,” or “September first,” but we should write “November 15,” “May 10,” and “September 1.”

In other words, although we pronounce dates using ordinal numbers, we should not write them that way. We should not write, for example, “November 15th,” “May 10th,” or “September 1st.”

By extension, when reading a date, perhaps “September 1, 1900,” we should read it as “September first, nineteen hundred” and not “September one, nineteen hundred.”

The exception to the rule

The only exception to this rule is when placing the number before the month. We would write “the first of September,” not “the one of September.”

Note that if you choose to write a date this way, avoid using numerals. It’s best to write out the number in this case. Rather than “the 1st of December,” use “the first of December.”

Image: table showing correct and incorrect way of writing with dates

Why do we write dates one way but pronounce them another?

Well, that’s a good question. Why is there no egg in eggplant? How can a house burn up while it’s burning down? English has some funny inconsistencies, and how we read and write dates is one of them. (You can check out some others here.)

At least now you’ll know not to be inconsistent the next time you send out an invitation to the big game.