Historical clue formulations

• Sample group? — 2017-12-23
• Sommeliers, at times — 2011-12-03
• Intrepid palace employees — 2009-03-28
• Chefs, at times — 2006-01-15
• Pillsbury Bake-Off officials — 2001-04-15
• Some test participants — 1997-05-31
• Dictator's security force, perhaps — 1995-04-29