Historical clue formulations

• Users of locker rooms: Abbr. — 2015-04-14
• Olympians, e.g.: Abbr. — 2011-06-08
• Sports players: Abbr. — 2009-05-26
• Jocks: Abbr. — 2004-03-27
• Olympians: Abbr. — 2001-01-04