Historical clue formulations

• Xi follower — 2022-07-21
• Head of Olympus? — 2014-08-14
• Original opening to Homer's "Odyssey"? — 2013-05-26
• O — 2012-04-22
• A fraternity chapter — 2006-03-10
• Pi preceder — 2005-02-22
• Certain fraternity chapter — 2003-03-29