How you write the date depends on where you live. Most of the countries of the world write it day first, then month, then year, or dd/mm/yyyy. A few places put the year first, which is what computer programmers would prefer, and please don’t abbreviate the year. The U.S. is, once again, contrary in that we write the month first.
But even more than the U.S., there is one country whose date-keeping stands out: Canada. Canada accepts all types of date formats. From Prince Edward Island to Vancouver—you can pretty much write the date however you like. No holds barred. This obviously raises questions: how does this make sense? Do people really have no standard way of noting the days? Is this even legal?
Canada is trying to to standardize the date format, but it will take time. Read about dates and how they are written at Atlas Obscura.
The other two make sense. We first adopted the popular UK date format, but widely see and use the US one. As for yyyy-mm-dd... maybe we're just getting prepared for the Chinese takeover?
Granted, because of the potential for confusion over mm-dd and dd-mm here, whenever I have the chance I write the date non-numeric. Jun 09, 2015.
Instead, m/d/yy is commonly used in the USA. Though I often prefer to write the 3-letter month to avoid any possible confusion... Eg. Jan/7/2025. And across the world, on computers, anyone sane only EVER uses YYYY-MM-DD, since nothing else will sort correctly.