MR
<input type="text" name="date" placeholder="yyyy-mm-dd" onkeyup="
var date = this.value;
if (date.match(/^\d{4}$/) !== null) {
this.value = date + '-';
} else if (date.match(/^\d{4}\-\d{2}$/) !== null) {
this.value = date + '-';
}" maxlength="10">