I seem to remember that there is a letter existing, between Alfred the Great in England and Charlemagne, which talks about importing mill stones - an odd thing to fake, if you were going to fake the existance of Charlemagne, I would have thought.
why oh why would alfred the great and charlemagne be coresponding since charlegmagne died in 814 and Alfred was born in 849. was chuck writing from beyond the grave?


anyway, my suspision was more about the year 800 than the xmas day. particularly, if you follow charlemagnes story that he had no idea that the pope had planned to crown him that day. charles was far too powerful to be crowed against his will anyway, as he claimed.
im not saying i support the theory one way or another, im just asking for more info about the theory. im also pointing out that the dark ages would be much easier to fake than say medievil times or the roman empire due to the dearth of sources.