Historical clue formulations

• Colleague of 23-Down for 15 years — 2018-09-21
• Justice replaced by Sotomayor — 2009-11-25
• Brennan's successor on the Supreme Court — 2009-07-25
• Supreme Court Justice David — 2000-12-04
• Justice from New Hampshire — 1998-03-04
• Justice who replaced Brennan — 1997-07-30