Historical clue formulations

• Indubitably — 2023-04-09
• Undoubtedly — 2013-07-26
• "No doubt" — 2011-05-23
• "Indeed!" — 2008-04-18
• Admittedly — 2003-03-08
• "Of course ..." — 2001-11-08
• Yea — 1997-01-01