JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://code.jquery.com/jquery-1.11.0.min.js"></script>
<script src="http://momentjs.com/downloads/moment-with-langs.min.js"></script>
<label for="id_nested-0-name">Name</label>
<input id="id_nested-0-name" maxlength="200" name="nested-0-name" type="text" />

<label for="id_nested-0-birthdate">Birthdate</label>
<input class="dateinput" datadatepicker="datepicker" id="id_nested-0-birthdate" name="nested-0-birthdate" type="date" />

<!-- New person -->
<label for="id_nested-1-name">Name</label>
<input id="id_nested-1-name" maxlength="200" name="nested-1-name" type="text" />

<label for="id_nested-1-birthdate">Birthdate</label>
<input class="dateinput" datadatepicker="datepicker" id="id_nested-1-birthdate" name="nested-1-birthdate" type="date" />

<div id="out"></div>

JavaScript

$(function(){
    $(".dateinput").click(function(){
        var diff = moment().diff(moment($(this).val()), 'years');    
        if( isNaN(diff) ){
            $("#out").html("Not a date<br/>");
            return;
        }
        if( diff >= 50 ){
            $("#out").html("Old geezer detected<br/>");
        } else {
            $("#out").html("Young slab detected<br/>");
        }
    });
});