Historical clue formulations

• Nixon in 1995 or Lincoln in 2012 — 2017-01-05
• Aida in "Aida," e.g. — 2016-03-04
• Top part — 2005-07-14
• Lulu in "Lulu," e.g. — 2004-01-16
• Lead, often — 2003-10-04
• Aida or Carmen — 2001-02-03
• Lead, often — 1998-07-04
• Biggest part, usually — 1998-05-30