Historical clue formulations

• Lunar phenomenon — 2020-09-17
• Nighttime event in the western sky — 2018-02-18
• Horizon happening — 2008-10-10
• Lunar disappearance — 2000-12-26
• Nighttime view — 1999-07-19
• Evening event — 1998-06-28
• Astronomical phenomenon — 1998-02-25
• Evening event — 1994-10-13