Demo no - 41 - Codepedia

Edit This Code :
<html>
<body>
<input type="date" id="txtStartDate" /> 
<input type="date" id="txtEndDate" /> 
<button id="btnCalculate2"  onclick="fnCalculateAgeFromGivesDates();" >Calculate Age</button>

<script>
function fnCalculateAgeFromGivesDates(){
    var startDateInput = document.getElementById("txtStartDate").value;  
    var endDateInput = document.getElementById("txtEndDate").value;  	 
	 
    // convert user input values into date object
	var startDate = new Date(startDateInput);
	var endDate  = new Date(endDateInput);
	 	 
	// get difference between two date;
	var difference=endDate - startDate.getTime(); 
	 	 
	var  ageDate = new Date(difference); 
	var calculatedAge=   Math.abs(ageDate.getUTCFullYear() - 1970);
	alert(calculatedAge);
}

</script>
</body>
</html>
Result :