Historical clue formulations

• D flat equivalent — 2026-01-20
• Optometrist's favorite musical note? — 2017-05-20
• D preceder — 2014-07-19
• Key for someone with 20/20 vision? — 2012-05-25
• D flat equivalent — 2012-04-04
• D preceder — 2011-04-24
• Black key — 2005-10-19
• D flat's equivalent — 2002-06-24
• The key of E major has one — 2001-09-29