A copy of the JavaScript functions in the head element:

// sample-6-diference.js
// display the difference between two dates

// display the input date in several formats
function display()
  {
  // First number - A
  var inputA1  = document.getElementById("inputA1");
  var inputA2  = document.getElementById("inputA2");
  var inputA3  = document.getElementById("inputA3");
  // convert value strings to numbers
  var input_valueA1 = new Number(inputA1.value);
  var input_valueA2 = new Number(inputA2.value);
  var input_valueA3 = new Number(inputA3.value);
  // three numeric arguments passed to the Date constructor
  var dateA   = new Date(input_valueA1,input_valueA2,input_valueA3);

  // Second number - B
  var inputB1  = document.getElementById("inputB1");
  var inputB2  = document.getElementById("inputB2");
  var inputB3  = document.getElementById("inputB3");
  var output1 = document.getElementById("output1");
  // convert value strings to numbers
  var input_valueB1 = new Number(inputB1.value);
  var input_valueB2 = new Number(inputB2.value);
  var input_valueB3 = new Number(inputB3.value);
  // three numeric arguments passed to the Date constructor
  var dateB   = new Date(input_valueB1,input_valueB2,input_valueB3);

  // compute result
  output1.value = dateB.getTime() - dateA.getTime();
  }