Historical clue formulations

• U.S. president with a Nobel Peace Prize — 2018-09-26
• 2002 Peace Nobelist — 2005-05-22
• #39 in a series — 2004-04-23
• SALT II signer — 2000-03-05
• # 6 ("Gomer Pyle, U.S.M.C.") — 1998-10-07
• Reagan's predecessor — 1996-12-16