Historical clue formulations

• Is serious — 2025-05-30
• Is serious — 2021-06-04
• Is dead serious — 2018-01-04
• Isn't fooling — 2016-03-26
• Isn't joking — 2005-12-18
• Isn't kidding — 2000-07-08
• Is serious — 1996-08-06