// Use Javascript
var today = new Date();
var dd = today.getDate();
var mm = today.getMonth()+1; //January is 0 so need to add 1 to make it 1!
var yyyy = today.getFullYear();
if(dd<10){
  dd='0'+dd
} 
if(mm<10){
  mm='0'+mm
} 

today = yyyy+'-'+mm+'-'+dd;
document.getElementById("datefield").setAttribute("min", today);