Historical clue formulations

• Grading option — 2023-07-30
• Grade option that doesn't affect one's grade point average — 2012-12-05
• Course option — 2007-04-08
• 64-Across's option for a 38-Across or a 13-, 18-, 28- or 42-Down — 2004-04-21
• Basic grading system — 2000-05-11