Historical clue formulations

• Proved useful — 2026-06-06
• Served — 2019-03-22
• Was of use — 2001-01-03
• Was of use — 2000-01-10
• Helped — 2000-01-08
• Helped — 1998-09-12
• Served — 1997-09-11
• Helped — 1996-02-18
• Was useful — 1995-01-12