Historical clue formulations

• Absolutely necessary — 2024-03-24
• Something critical to have — 2023-12-02
• Something absolutely necessary — 2022-03-20
• Something required — 2018-12-30
• Something absolutely necessary — 2017-11-12
• Something necessary — 2017-03-07
• Something that's not optional — 2010-12-26
• Something that can't be missed — 2010-12-08
• Not to be missed — 2006-05-11
• Not to be missed — 2005-09-10
• "___ to Avoid" (1966 hit) — 2000-08-03
• Imperative — 1994-06-18