Change your default date format to the least ambiguous

On 13th November 2025 a TikTok-er had beef with Air Canada.¹

She claimed her food was prepared months six months before being served. The packet was marked:

To much of the planet this date reads 5th November 2025 but to US Americans it reads as 11th May 2025. So the beef was actually prepared eight days earlier and because people on the internet are bullies she was publicly mocked by millions of people.

I believe this confusion could have been avoided if Air Canada's in-flight meals had less ambiguous dates. I also believe we can learn from this mistake to marginally improve our lives.

Changing your default date format to the least ambiguous prevents confusion, saves time and mental energy parsing dates, and may even prevent global humiliation.

What is the easiest to parse and least ambiguous date format?

For a date format to be easy to parse and unambiguous it should satisfy these criteria:

1. Immediately be identifiable as a date. Maybe it's a reference number, a verification code, or maybe you're just friends.
2. Have a clear distinction between days, months, and years.
3. The dates should make no sense if you confuse it with another date format

We'll start with the most ambiguous and build it up to something easier to understand.

A date written like this is pretty useless if you're not a computer. It could mean anything at all. Luckily you don't see this sort of thing very often outside of order reference numbers.

Delimiters

To make it more date-ish we can add delimiters between the numbers…

Those look more like dates as dates are always three numbers, but they could still be interpreted as a sort code, a version number, or something like that.

Long year

If we add the number 20 to the beginning of the year, we get…

Now it definitely looks like a date because the last part is recognisable as a year we just had.

If we add the word BEEF to the beginning of it, we get what was printed on the in flight meal. But we still have to fix the day and the month being confused.

Adding the name of the month

By using the name of the month instead of a number we make it impossible to confuse it with the day.

Now that 05 and 2025 are separate by a word we can make this a little easier to look at by replacing the slashes with spaces.

We can optionally save Air Canada millions in ink by using the three letter abbreviation of the month.

Ordinal indicators

If you want to make it super easy for your eye balls to recognise which part of the date is which, you can add ordinal indicators to the day and remove the preceding zero.

Months and years never have ordinal indicators so your brain knows it must be the day.

This is the perfect date format. Even if you mixed it up completely it would still be understandable.

Language barriers

The major downside of using dates with the month names and ordinal indicators is language barriers.

A non-english speaker may be forced to translate these dates and that's not fair.

Here's the same date written in French:

It's even harder to guess the meaning if the language doesn't share an alphabet.

(Nobody would ever actually write the date like this in Japanese, but if they did you would find it difficult to understand in a similar way to how a non-english Japanese speaker would find Beef 5th November 2025 difficult to understand.)

What if you can only use numbers?

Some software doesn't allow you to use dates with words or ordinal indicators. So what's the best numbers and delimiters only format?

Endianness

The most important consideration is endianness. Endianness means which end comes first. Something is big-endian if the big end (the year) comes first and little-endian if the little end (the day) comes first.

So 2025-11-05 is big-endian and 05-11-2025 is little-endian.

Either one of these formats would work great if it weren't that for unfathomable reasons the USA uses middle-endian. The month first, followed by the day, followed by the year, e.g. 11-05-2025 which can be easily confused with little-endian dates which is exactly what happened with the airplane beef.

Luckily for humanity, nobody uses middle-endian the other way round e.g. year-day-month so big endian with the long version of the year can't be confused with middle-endian.²

So the most reasonable choice to prevent confusion is big-endian.

A useful advantage of big-endian dates

Big-endian dates have another advantage over other date formats.

When you sort them in lexicographical order (alphabetical order including numbers and symbols) they also line up in chronological order. So on a computer file system, if your file names start with dates and you sort them by name, the files will be in chronological order.

Slashes, dots, or hyphens

I grew up with slashes between my numbers so I think they make a date look more like a date — but different strokes are preferred by different people and places.

One problem with slashes is they don't create enough empty space between the numbers — the numbers and the slashes all blur together into a single block of text. Dots and hyphens don't have this problem.

Dots and slashes also share a new problem in the information era – they cause confusion when you name a file or a web page using a date…

images/beef-2025.11.05.jpeg

images/beef-2025/11/05.jpeg

In many cases software will reject file names.

So to maintain consistency across all your date usage I recommend hyphens. This also happens to be the recommendation of ISO 8601⁴ — so each time you write a date you can feel the comfort of International Organization for Standardization cradling you with it's big strong arms.

Winning date formats

The date format award for most readable by humans who share a language…

The date format award for most compatible with the most humans and computers too…

How to change the default date format on MacOS

1. Open System Settings
2. Navigate to General
3. Navigate to Language & Region
4. Tap the dropdown next to Date format and select the date format.

How to change the default date format on iOS

1. Open Settings
2. Navigate to General
3. Navigate to Language and Region
4. Tap Date Format
5. Select the the date format of your choice.

Tags

• organization
• organization
• saving time
• computers

Published

23 Feb 2026

Updated

23 Feb 2026