Final answer:
Without additional context, it is not possible to determine the specific time when 'Richard's army' left Sicily. For Richard the Lionheart, it was in the late 12th century during the Third Crusade, more precisely 1191.
Step-by-step explanation:
The question "When did Richard's army leave Sicily?" does not provide a clear context regarding which historical figure named Richard is being referred to. Therefore, it's not possible to provide a specific date without additional information. If this is referring to Richard the Lionheart during the Third Crusade, his armies left Sicily in the late 12th century. Richard landed in Sicily in 1190 and departed from there the next year, ultimately heading towards the Holy Land. However, if we are discussing other historical events or figures, the timing would differ significantly.