Historical clue formulations

• Tilted, in Stilton — 2019-03-31
• Wasn't straight up — 2018-01-21
• Inclined — 2015-04-29
• Had an inclination — 2013-06-01
• Was biased — 2011-09-20
• Inclined — 2011-06-29
• Inclined — 2010-08-19
• Wasn't quite vertical — 2008-04-23
• Was biased — 2004-04-16
• Inclined — 2003-11-17
• Tilted, once — 2003-09-23
• Rested — 2003-05-24
• Wasn't erect — 2002-04-24
• Wasn't upright — 1997-09-28
• Wasn't upright — 1996-08-21
• Inclined — 1996-08-20
• Canted — 1996-03-10
• Inclined — 1995-06-10
• Inclined — 1994-12-18
• Listed — 1993-12-24