The ISO-7813 standard recommends MM-YY or MM/YY as the proper way to format credit card expiration dates. That’s why all credit card expiration dates have two digits for the month and two digits for the year.

When implementing the same on your store’s credit card form, you need to follow the same principle. Don’t use month names or 4-digit representations for the year. Have 10 instead of October, and have 23 instead of 2023. Double digit numerals should also be used for single numbered months. That means 07 instead of 7.

Why?

It’s more convenient for customers. The expiration dates appeared on their credit cards formatted as MM-YY or MM/YY and entering it as it appears is the quickest method. The fewer mental conversions they have to perform, the quicker they can fill out the form and check out.

This also reduces errors. According to a study by the Baymard Institute, a small minority of customers don’t instinctively know the link between month names and numbers.

A subject in their study resorted to counting his fingers in order to determine what number the month of August corresponds with. Nearly everyone knows August is the eighth month but there are a few people who don’t. Since the number is larger than five, he has to use both hands in the count. If he makes an error and skips a thumb during his finger-counting he’s going to enter wrong information (either seven or nine).

We could blame the education system all day, but making things as simple as possible is the commercially smart decision.