Historical clue formulations

• The "one" in "the old one-two," maybe — 2019-06-28
• One, in a one-two punch — 2019-03-23
• It might be followed by a right hook — 2015-04-15
• Delivery that may floor you — 2010-10-08
• Southpaw's hit — 2006-06-15
• Start of a one-two punch — 2002-06-16