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                <h1 class=c>On what day of the week were you born?</h1>

<div class=c>
<b><p>Please Enter your birthday</b> (then click the <b>&ldquo;Update&rdquo;</b> 

<form onreset="messagesElt.innerHTML = '&nbsp;';">
  <p>Numeric Month (1-12): <input TYPE="number" NAME="Inputmonth" value="12">  
  &nbsp;&nbsp;Day of Month (1-31): <input TYPE="number" NAME="Inputday"value="27">     
  &nbsp;&nbsp;Year (e.g. 1960): <input TYPE="number" NAME="Inputyear" value="1990">   
  &nbsp;&nbsp;<input TYPE="button" VALUE="Update" ONCLICK="compute(this.form)"> 
	<input TYPE="reset" VALUE="Clear"> </p>
<p id="messages">&nbsp;</p>
<!-- Output Age in Years Months and Days Format -->
  <p>Today You Are: <input TYPE="text" NAME="AgeYMD" SIZE="58" readonly></p>

<hr size="3" noshade color="#F00000">

<br />
<p>If you find this demo useful, please consider <a href="" target="_blank">donating $1 dollar</a> for a coffee using the button below or purchasing one of my songs from <a href="" target="_blank"></a> or <a href="" target="_blank"></a> for only 0.99 cents each. I have also released CDs with my band <a href="" target="_blank">Ivory Knight</a> and Annihilator main-man Jeff Waters.</p>
<p>Rob uses and recommends <a href="" target="_blank">MochaHost</a>, which provides Web Hosting for as low as $1.95 per month, as well as unlimited emails and disk space!</p>


                body { background-color: lightgray; font-family: Arial, sans-serif; font-size: 16px; }

.c	{ text-align: center; }

h1 { 
  font-size: 1.5em !important; 
  font-style: italic; 
  color: #004080;

input[type="text"], input[type='number'], input[type="date"] { font-size:18px; }
input[type="number"] { width: 75px; }
input[readonly] { background-color: #dedede; border: none; }

#messages    { color: red; }


                var messagesElt = document.getElementById('messages');

String.prototype.singularize = function(num) {
  return (num == 1 ? this.slice(0, -1) : this);

Date.getFormattedDateDiff2 = function(date1, date2, intervals) {
  var b    = moment(date1),
      a    = moment(date2),
      dur  = moment.duration(a.diff(b)),
      out  = [];
  intervals.forEach(function(interval) {
    var intervalDuration = dur[interval]();
    //unlike the other getters for duration, weeks are counted
    //as a subset of the days, and are not taken off the days count.
    if (interval == 'days') intervalDuration %= 7;
    out.push(intervalDuration + ' ' +  interval.singularize(intervalDuration));
  return out.join(', ');
Date.getFormattedDateDiff = function(date1, date2, intervals) {
  var b = moment(date1),
      a = moment(date2),
      intervals = intervals || ['years','months','weeks','days'],
      out = [];

  intervals.forEach(function(interval) {
      var diff = a.diff(b, interval);
      b.add(diff, interval);
      out.push(diff + ' ' + interval.singularize(diff));
  return out.join(', ');

function getBirthday(Inputyear, Inputmonth, Inputday) {
   var inputYear  = parseInt(Inputyear.value),
       inputMonth = parseInt(Inputmonth.value),
       inputDay   = parseInt(Inputday.value),
   if ( isNaN(inputDay) ) {
      messagesElt.innerText = 'Invalid day.';
   else if ( isNaN(inputMonth) ) {
     messagesElt.innerText = 'Invalid month.';
   else if (inputMonth < 1 || inputMonth > 12) {
      messagesElt.innerText = "Month is out of range";
   else if ( isNaN(inputYear) ) {
     messagesElt.innerText = 'Invalid year.';
   else if (inputYear < 1900) {
      messagesElt.innerText = "You're that old!?";
   else {
     var tempBirthday = moment([inputYear, inputMonth-1, inputDay]);
     if ( tempBirthday.isValid() ) {
       if ( tempBirthday.diff(new Date(), 'days') < 0 ) {
         birthday = tempBirthday;
       else {
         messagesElt.innerText = "Your birthdate must be in the past!";
     else if ( tempBirthday.invalidAt(2) ) {  //month overflow
        messagesElt.innerText = "Day is out of range";
   return birthday;

function compute(form) {
   messagesElt.innerHTML = '&nbsp;';
   var today       = moment(new Date()),
       birthday    = getBirthday(form.Inputyear, form.Inputmonth, form.Inputday);
   if (!birthday) return;
   form.AgeYMD.value   = Date.getFormattedDateDiff( birthday, today );