Historical clue formulations

• TV sets? — 2021-01-01
• Subjects of four famous violin concertos by Vivaldi — 2020-05-17
• Units for binge watchers — 2017-12-17
• Flavors — 2017-04-23
• Collections of episodes — 2016-01-15
• Noted quartet — 2015-05-06
• Annual quartet — 2012-05-06
• Annual foursome — 2010-05-30
• Years on the diamond — 2008-09-07
• Calendar divisions — 2008-05-11
• Annual quartet — 2002-02-01
• Peppers, perhaps — 2000-08-31
• Annual foursome — 1998-08-02