Historical clue formulations

• "Is that ___?" — 2010-01-17
• "It's ___" ("There's no doubt") — 2008-03-03
• "Is that ___?" — 2007-04-29
• "Is that ___?" ("Really?") — 1998-06-23
• "Is that ___?!" — 1997-04-03
• "Is that _____?" ("You don't say!") — 1995-08-27