Historical clue formulations

• First of four emperors in the "Year of the Four Emperors" — 2025-01-11
• Emperor after Nero — 2015-09-12
• Emperor after Nero — 2009-10-12
• Nero's successor as emperor — 2004-11-12
• Emperor after Nero — 2003-11-11
• Nero's successor — 2001-01-07
• Nero's successor — 1997-08-24