Historical clue formulations

• Showed sleepiness — 2024-09-20
• Silently assented — 2015-01-27
• O.K.'d silently — 2014-09-29
• Dozed (off) — 2013-08-20
• Signed an agreement? — 2005-04-29
• Goofed — 2004-02-22
• Agreed silently — 2001-12-03
• Let a slip pass — 2000-01-27
• Bid, perhaps — 1999-07-23
• Erred through oversight — 1996-03-24
• Signaled assent — 1995-09-21