For filing purposes? Year is the first sorting criterion, duh. That doesn't necessarily mean it needs to be listed at the beginning in the handwritten form - you'll see it just as quickly at the end. (It is no coincidence that none of these formats listed have the year in the middle.
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As for everyday writing? Well, whatever you're used to and your readers will expect, just as with the comma/point thingy. Though there's a slight difference in that mm-dd-yyyy is really almost as illogical as putting the year in the middle, and I haven't the slightest clue how it came to be (while with the numbers, it's all convention anyways).
Poll
