In earlier versions of OS X, setting your date format to have the day before the month was sufficient to also alter the default paper size to A4, which was really inconvenient for me since I prefer the day-month ordering (and as a consequence of buying a digital watch in the Netherlands which only had instructions in Dutch which I didn’t understand, I developed the habit of using 24 hour time), but I live in the US and only rarely encounter paper which isn’t 8.5x11.

Don't you mean paper which isn't 215.9 by 279.4 mm?

Go on, switch your thermostat in the US to degrees C. Join us.