Historical clue formulations

• Letter before zee — 2017-02-14
• ___ Accord (1998 Mideast peace agreement) — 2010-03-25
• Ex follower — 2007-11-04
• Slingshot's shape — 2007-07-08
• Letter between ex and zee — 2006-05-22
• ___ Accord (1998 peace agreement) — 2000-02-24
• ___ peace accord (1998 agreement) — 1999-09-28
• ___ Accords (1998 peace agreement) — 1999-01-24
• Penultimate letter — 1998-04-16
• Fourth of July? — 1997-02-09
• Pipe joint — 1995-03-05
• Three-way circuit — 1995-02-07
• Penultimate letter — 1994-08-28
• Fork — 1993-12-28