Historical clue formulations

• Divisions in some history books — 2025-07-15
• Subjects of VH1's "I Love the ..." series — 2023-03-05
• A long, long time — 2021-12-30
• Divisions of a century — 2014-07-21
• The 1980s and '90s, e.g. — 2014-05-28
• They take years to end — 2011-01-15
• Years of plenty — 2010-04-01
• The Roaring 20's and others — 2000-08-01