Historical clue formulations

• French painter Henri known for "The Sleeping Gypsy" — 2018-06-19
• Philosopher who wrote "To be sane in a world of madmen is in itself madness" — 2017-03-26
• "The Social Contract" philosopher — 2011-11-27
• "The Sleeping Gypsy" painter — 2011-01-27
• "The Social Contract" philosopher — 2005-09-18
• "The Sleeping Gypsy" painter — 2000-05-14
• "The Social Contract" philosopher — 1999-08-27