Historical clue formulations

• Resign — 2013-01-18
• Abdicate — 2011-07-10
• Relinquish — 2008-02-17
• Relinquish — 2007-08-04
• Relinquish — 2004-06-20
• Resign, as a job — 2003-05-16
• Call it quits — 1997-12-28
• Resign, as an office — 1997-04-27
• Relinquish — 1996-12-27