Edson,
I think you'll need to change the placeholder in the advanced properties:
Take a look at the link below:
https://github.com/RobinHerbots/Inputmask#placeholder-1
Try to place the code below, changing the format according the current locale. Maybe you'll need a auxiliar function to return that format.
{ "placeholder": "dd/mm/yyyy" }
Tell us if it helps.
Cheers.