Historical clue formulations

• Step 2: Partygoer's guest — 2023-08-14
• Date for a party — 2022-09-01
• Wedding guest's partner, say — 2022-04-19
• Guest's guest — 2020-11-29
• Unidentified date — 2019-05-08
• With a guest, on a guest list — 2017-11-03
• Valence of sodium — 1999-07-17