Historical clue formulations

• Eternal — 2023-07-10
• Eternal — 2020-09-07
• Forever young — 2014-05-04
• Eternal ... and a hint to 19-, 34-, 42- and 55-Across — 2008-08-21
• Opposite of ephemeral — 2007-07-21
• Undying — 2002-11-08
• Never outdated — 2001-03-09
• Perpetual — 2001-02-25
• Undying — 1999-01-06
• Undying — 1997-04-12
• Untouched by time — 1996-04-26