Historical clue formulations

• Spelunker — 2026-06-29
• Subterranean adventurer — 2026-02-01
• Speleologist — 2018-07-14
• Speleologist — 2018-06-06
• One who's frequently in the dark — 2018-02-16
• Spelunker — 2014-01-01
• Explorer of sorts — 2008-05-18
• Spelunker — 1999-03-22
• Speleologist — 1998-09-12
• Spelunker — 1995-12-19