

I wondered whether maybe the us americans had continued using the old style and it was Britain that changed, but no: Britain appears to have been using the day-month-year order since medieval times. This latin letter from William Wallace from 1297 has that order: https://www.wikitree.com/wiki/Space:Lubeck_Letter
*Given at Haddington in Scotland on the eleventh day of October in the Year of Grace one thousand two hundred and ninety seven. *
The latin line with the date starts with “datum”.
Great find.
I checked a few other historic front pages on Wikipedia: https://en.m.wikipedia.org/wiki/List_of_the_oldest_newspapers The Oxford Gazette from 1665 used the same month-day format. The first edition from The Guardian from 1821 also used it. Some British news papers like The Times never stopped using it, while The Guardian is now using day-month. So it was the British after all.