Historical clue formulations

• Piece of the pie, perhaps — 2021-02-25
• One-eighth portion — 2020-01-13
• One-eighth of a circle — 2019-05-22
• One eighth — 2017-01-06
• Piece of pie, often — 2009-01-10
• Navigational instrument — 2003-09-14
• 45-degree sector — 1994-04-09