How many years since April 15 1450? Leonardo D'Avi

Leonardo D'Avinci was born April 15, 1450.
I was born April 15, 1950.
5 centuries before me?
Not true.
But your calculator does not go that far.
Complicated, but could you add changes in the calendar?
Also the calendar changes did not happen everywhere at the same time.

Would be nice to calculate difference in time since April 1. 1500 in Venice and April 1, 1800 in Paris.