The semicircle at the top of each page shows astrological and astronomical data.
Explanation:
In Très Riches Heures du Duc de Berry, there are a number of full page images, which also include calendar images. What we might notice is that there is a semicircle at the top of each page. This semicircle shows astrological and astronomical data. It is included because stars were integrally tied to the agricultural calendar. Moreover, many medical specialists used to believe that a person's health is somehow also related to the pattern of stars of the day he/she was born.
