Historical clue formulations

• Subjects of some Billboard charts — 2026-07-21
• Reunion attendees — 2016-10-27
• iTunes category — 2016-04-24
• Some collectors' "vinyl" — 2014-09-10
• Contents of sleeves — 2010-08-15
• iPod heading — 2010-02-28
• Photo groups on Facebook — 2010-01-03
• They have many cuts, typically — 2007-03-17
• Philatelists' books — 2005-08-23
• Picture books — 2003-06-24
• Picture holders — 1998-01-08