Onchange didn't show or hide Div

I've a problem with my Script, please take a look.

My Javascript

<script type="text/javascript">
$(document).ready(function()
{
    $("#datetimepicker_mask2").change(function() 
    { 
    var tanggalnya = $("#datetimepicker_mask2").val();
        $.ajax({ 
        type: "POST", 
        url: "http://localhost:84/helpdesk2/forgot_password/check_date/"+tanggalnya,
        success: function(msgtgl){ 
        if(msgtgl === 'benar' ){
            console.log(msgtgl);
            $('#form_email').show();
            }
        else
            {                   
            console.log(msgtgl);
            $('#form_email').hide();;
            }
        }
    });
retu false;
    });
    });
</script>

My HTML

<div class="login-box-body">
    <div id="form_email">
      <form action="http://localhost:84/helpdesk2/forgot_password/check_date/" method="post">
    <div class="form-group has-feedback">
            <input class="form-control" id="email" placeholder="email@domain.com" name="email" />
            <span class="glyphicon glyphicon-envelope form-control-feedback"></span>
    </div>
            </div>
            <div id="hasiltanggal"></div>
        </div>

I can't show my form_email. I wonder why, because in console.log(msgtgl) i receive benar. So, the form_email should be showed up, right?