Q:

HTML 5 Bug Input Type Date POST Form

<?php
    if(isset($_POST['VACA_INI'])){echo  "<br>" . $_POST['VACA_INI'];}
    else{echo "<br> .... NO POST VACA_INI .....";}

    if(isset($_POST['VACA_FIN'])){echo  "<br>" . $_POST['VACA_FIN'];}
    else{echo "<br> .... NO POST VACA_FIN .....";}

    if(isset($_POST['aaa'])){echo  "<br>" . $_POST['aaa'];}
    else{echo "<br> .... No he recibido el aaa .....";}
?>
<!doctype html>
<html class="">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>....</title>
</head>
<body>
<form name="Vacas" id="Vacas"  method="post" action="">
<input type="text" id="aaa" name="aaa" value="aaa">
<input type="date"  id="VACA_INI"  required value="2018-02-02"  ></div>
<input type="date"  id="VACA_FIN" value="2018-02-02"  required >
<button id="Enviar" name="Enviar" type="submit" class="btn btn-primary">Enviar</button>
</form>
</body>
</html>

Return:
.... NO POST VACA_INI .....
.... NO POST VACA_FIN .....
aaa
chrome: Versión 63.0.3239.132 (Build oficial) (64 bits)

A:

Input don't have the corresponding name VACA_INI and VACA_FIN.
Also remove the </div> closing tag. 
<input type="date"  id="VACA_INI" name="VACA_INI" required value="2018-02-02"  >
<input type="date"  id="VACA_FIN" name="VACA_FIN"  value="2018-02-02"  required >

