Get Age Based On Year Entered

function calAge(bDay){

 var born;

 now = new Date()

 bD = bDay.value.split('-');

 if(bD.length!=3){

   alert('Date Is Not Valid'); 

  MyForm.age.value="";

 }

 else if(bD.length==3){

born = new Date(bD[2], bD[1]*1-1, bD[0]);

 years = Math.floor((now.getTime() - born.getTime()) / (365.25 * 24 * 60 * 60 * 1000));

    MyForm.age.value = years;

 }

}