Perhaps they are going to ask me to leave the country, but there are higher financial authorities than the Banque de France. The ECB stats also mention an average of 0.8061 for the year 2014:
" Change from 1 January 2014 to 31 December 2014
Minimum (30 September 2014): 0.77730 - Maximum (18 March 2014): 0.83830 - Average: 0.80612 "
Perhaps the boys and girls of the European Central Bank count every day as you already suppose because there is still some inequality among the months of the year: some are richer in days than others. From the viewpoint of the Egalité
as we can see on every Mairie here there is still some work to do to end this injustice. A retry for the French Republican Calendar
Even more homework: adding all daily exchange rates and dividing them by 365 to verify or falsify the underlying logics of the ECB counting methods. But for the moment I prefer to listen to Sam Cooke: Don't know much about algebra. Don't know what a slide rule is for.