Format HTML5 input calendar with javascript

I'm doing a form with validation in HTML5 and I came across a bit of a bad situation, when I put type="date" when I move the mouse over the "settlers" to manipulate date or ascend to the calendar. The problem is that the formatting is horrible and I would like to know if there is no way I can use CSS or JAVASCRIPT to solve this problem.

 <input type="date" name="DtNascimento" required="required" 
oninvalid="setCustomValidity('Por favor, digite sua Data de Nascimento.')" 
onChange="try{setCustomValidity('')}catch(e){}">