It was William of Malmesbury who cursed the "dangerous Saracen magic" of the zero in the 12th century, before which it did not exist in European numerical calculations.
Thus, Dionysius, who started the concept of Anno Domini, would have had no idea what those who think a zero indicates the beginning of any period were talking about. It was an alien concept that did not figure then and does not now, as we use the same basis for the calculation of our years as he did, even though our calendar has been updated. Surely this concept is no harder to grasp than it is for a year beginning with 19 having been in the 20th century?
ANDREW HN GRAY