As soon as word that the Emperor Julian of Constantinople, the last of the roman emperors to worship the Olympians, had been killed fighting the Persians in A.D. 363, Zeus was told by the Three Fates that his regin had ended - he and his godly family must leave Mount Olympus. In anger of this, Zeus destroyed Olympus with his mighty thunderbolt, and he and his family went off to lives among humble country people, hoping for better times.
Mortals were now allowed to reckon by weeks agian, as Prometheus the Titan had once taught them. The Olympians were forced to hide in woods and caves, and have not been seen for centeries.