Daniel 9:1

"In the first year of the reign of Darius son of Ahasuerus, a descendant of the Medes, who was made king over the kingdom of the Chaldeans

So Daniel remained there in service until the first year of King Cyrus.

and Darius the Mede took over the kingdom at the age of 62.

Daniel achieved success during the reigns of Darius and Cyrus the Persian.

Treasury of Scripture Knowledge

In the first year of Darius the son of Ahasuerus, of the seed of the Medes, which was made king over the realm of the Chaldeans;

So Daniel remained there in service until the first year of King Cyrus.

and Darius the Mede took over the kingdom at the age of 62.

It pleased Darius to appoint 120 regional authorities over the kingdom throughout the realm,