Error changing date

I am doing a system that is managed with dates, but the problem is when I want to change a date, example: I choose today's frecha and the one of the day 14-12-2018, in total they are 10 days which is going to me calculate a value for those 10 days, but when I want to change the date one more days before, I do not change the value.

<?php
date_default_timezone_set('America/Argentina/Buenos_Aires');
$tarjeta = 200;
$efectivo = $tarjeta*0.5;
?>

<script>
function data(valor) {
let ingreso = document.getElementById("ingreso").value;
let retiro = document.getElementById("retiro").value;
let fechaInicio = new Date(ingreso).getTime();
let fechaFin    = new Date(retiro).getTime();
let diff = fechaFin - fechaInicio; //Diferencia en milisegundos
let dias = diff/(1000*60*60*24); //Diferencia en dias
document.getElementById("totaldias").value = dias;
document.getElementById("valor").value = dias*valor;
document.getElementById("dolares").value = valor*tasa_cambio;
}

Form

<h2>Sistema</h2>
<form action="" method="post">
<input type="date" name="ingreso" id="ingreso" autocomplete="off"><br>
<input type="date" name="salida" id="retiro" autocomplete="off"><br>
<input type="radio" id="efectivo" name="pago" value="efectivo" onChange="data(<?php echo $tarjeta;?>)">
<label for="efectivo">Tarjeta 100%</label><br>
<input type="radio" id="tarjeta" name="pago" value="tarjeta" onChange="data(<?php echo $efectivo;?>)">
<label for="tarjeta">Tarjeta 50%</label><br>
<label for="totaldias">Total dias</label>
<input type="text" name="dias" id="totaldias" readonly="readonly"><br>
<label for="valor">A pagar</label>
<input type="text" name="valor" id="valor" readonly="readonly">
</form>