If you ask an American about the way their dates are formatted, you may get a response as defensive as 'my jumper is not on back to front, it's supposed to have the v at the back!'.

But let's face it, it's weird. Basic group behaviour shows it's weird. Despite the variety of date formats used around world, the US is the only country to insist on using mm-dd-yyyy.

Date formats around the world

Image: John Harding/Mona Chalabi

This condition is diagnosed as middle-endianness. Seriously. It comes from computer science where bytes are arranged according to their size. If the order has larger ones at the front, it's known as big-endian and so too are dates formatted with the years first (see the likes of China and Mongolia in the map above).

Even more bizarrely, computer scientists got their inspiration for the term 'endianness' from Jonathan Swift's 1726 epic Gulliver’s Travels. In the fictional kingdom of Lilliput people have to open their soft-boiled eggs at the small end (it's a royal decree). While in Blefuscu, eggs are cracked from the other end. Lilliputians are small-endians while Blefuscudians are big-endians. Again, seriously.

Jonathan Swift, like the computer scientists, was basically saying that systems are needed to organise even the most irrelevant seeming of things. As Danny Cohen writes "Swift's point is that the difference between breaking the egg at the little-end and breaking it at the big-end is trivial… but we insist that everyone must do it in the same way, to avoid anarchy. Since the difference is trivial we may choose either way, but a decision must be made."

But why did Americans choose the way they did? Actually, the dozens and dozens of chat forums on the topic reveals that people don't really seem to have an answer. We don't. If you think you do, post a comment below to let us know. Though it seems that Googlers (most of them small-endians) are far more puzzled by other American choices.