Daniel 1:21

‘And Daniel continued, even to the first year of Cyrus the Persian.' The ‘first year of Cyrus the Persian' was an epochal day in the lives of the children of Israel, ranking possibly with the day of the giving of the Law at Sinai, for it probably means the year in which he became king over Babylon, and thus the year when the Babylonian dynasty ceased, and Israel's deliverance and ability to return from exile was announced. It refers to that year in which Cyrus made his decree that announced the end of the exile and that stated officially that the people could return home (Ezra 1:1).

So this verse is declaring that from the day of his acceptance by Nebuchadnezzar Daniel continued to have standing in the Babylonian court right up to its end in its overthrow at the hands of Cyrus, sixty six years or so after his being taken from Jerusalem. And for much of the time he was respected and admired by the kings of Babylon. He had a worthwhile career. It is also telling us that he lived through the whole of the exile until the decree that ended it. (Those events were considered far more important than his death. It is saying nothing about what followed those events, and in Daniel 10:1 we learn that Daniel was still alive in the third year of Cyrus).