The Hours of Charles of Angoulême

On the back of the remarkable Ave Maria in large initials is an equally unusual diagram which must originally have been even more striking than it is now. At the outset, the vivid colours of the concentric circles behind the diagram must have stood out more clearly against the cream-coloured parchment. Indeed, one of the components used to make the golden ground of the Ave Maria, probably silver, has gone rusty and seeped deep into the parchment. The diagram consists of spokes extending from a circle in the centre decorated with a sun to two outer circles bearing instructions about how to use the diagram. The main spoke, at the top, contains a sequence of Roman numerals in red ink from I to XIX: the golden number used to calculate the dates of the new moon and, therefore, Easter. Written on the other seven spokes are the possible dates of Easter, calculated by using the golden number of each year.