For centuries, Vincent de Paul’s birth year was held to be 1576. Pierre Coste’s research established that it was actually 1581, and that Vincent knew his age and referred to it consistently. There are many reasons for the five-year difference in tradition. As was common at the time, Vincent lied about his age at ordination, being nineteen and not the requisite age of twenty-four. Early biographers either left his comments about his age undated or tampered with sources to make them add up to his traditional age of eighty-five at his death.
Slawson, Douglas C.M.
"The Phantom Five Years,"
Vincentian Heritage Journal: Vol. 2
, Article 5.
Available at: http://via.library.depaul.edu/vhj/vol2/iss1/5