Most everyone alive today is aware that it's 2019 according to the Gregorian Calendar. Did the average French farmer in 1400 know or care that it was 1400 (according to the Julian calendar I think at this point)? Or was it more educated people who were aware or interested in such things?
Not to discourage further responses, but you might be interested in this answer by /u/Algernon_Asimov, which also links to a couple other similar posts. For further reading (on the subreddit), there is a calendar section of the FAQ