I've been trying to add placeholder in input type='datetime-local' field but it doesn't work at all. Use css for solving the issue but still unable to do it :(
input[type="datetime-local"]:before{
content: 'Selecteer Datum';
color: #000;
text-align: center;
width:100%;
}
input[type="datetime-local"]:active:before, input[type="datetime-local"]:hover:before, input[type="datetime-local"]:visited:before, input[type="datetime-local"]:focus:before{
content: '';
width: 100%;
}
<form action="" method="post">
<div class="datetime">
<input type="datetime-local" >
</div>
</form>