Historical clue formulations

• One of the Teenage Mutant Ninja Turtles — 2017-10-04
• Mathematician Fibonacci — 2015-08-30
• DiCaprio who played half of 67-Down — 2012-11-18
• "Vitruvian Man" artist — 2010-08-15
• Kate's "Titanic" co-star — 2001-09-10
• "Mona Lisa" painter — 2001-05-21