Historical clue formulations

• Flowering herb also known as devil's nettle — 2018-12-23
• Peter of Peter, Paul and Mary — 2016-09-13
• Peter of Peter, Paul and Mary — 2015-06-10
• Peter of Peter, Paul and Mary — 2013-02-12
• Peter of Peter, Paul & Mary — 2007-10-15
• Peter who wrote "Puff the Magic Dragon" — 2006-02-05
• Peter of Peter, Paul and Mary — 2004-09-08
• Peter of Peter, Paul & Mary — 1998-03-10
• Peter of Peter, Paul & Mary — 1995-03-20