Answer based on context:

The Siege of St. Dizier took place in the summer of 1544, during the Italian War of 1542-46, when the Imperial army of Charles V attacked the French city of St. Dizier at the beginning of its advance into Champagne. The siege was already underway when Charles V himself arrived with an army of 14,100  on July 13. The next day an imperial commander, René of Châlon, Prince of Orange, was struck by a shot from the defenders, and died the next day with the Emperor by his bed . On July 23 French outposts near the besieged town were overrun, but a French army under the command of the Dauphin Henry maintained an observing position at Jalons. On August 17 the town surrendered. Charles elected not to attack the Dauphin's army and instead pressed on to Soissons.

What day did Rene of Chalon die?
-July-15