Historical clue formulations

• *Dmitri Ivanovich Mendeleev and Julius Lothar Meyer — 2018-08-08
• Science class decoration — 2009-05-08
• Chemistry class poster, perhaps — 2008-09-30
• Place for I, O or U — 2006-03-24
• Occasional furniture? — 2004-11-18
• It begins with H — 2000-06-28