Historical clue formulations

• Spicy pretzel dip — 2013-03-07
• Condiment at Nathan's — 2010-10-19
• Colonel suspected of murder — 2009-07-15
• 40-Across/34-Down topping — 2003-09-11
• Kind of gas — 2000-07-26
• Colonel on the board — 1994-04-24