Historical clue formulations

• As a joke — 2026-07-12
• For yuks — 2024-09-11
• For laughs — 2017-04-23
• Humorously — 2015-02-07
• Kiddingly — 2010-11-03
• How quips are delivered — 2009-06-01
• Kiddingly — 1996-12-06
• Kiddingly — 1996-02-20