Erasmus, important for psychiatry?

It is supposed, that Erasmus of Rotterdam, the great humanist, was bom 500 years ago in 1469. Why? Erasmus himself many times gives another year of birth. Why?
We have tried to make this clear. In the same time we have considered the question this briljant philologer has contributed to psychiatry. His most important work — the praise of foolishness — world suggest so.