$dt = new Carbon\Carbon();
$before = $dt->subYears(13)->format('Y-m-d');
$rules = [
...
'dob' => 'required|date|before:' . $before
];
---------------
Different Solution (Enhanced)
use Carbon\Carbon;
$dt = new Carbon();
$before18Years = $dt->subYears(18)->format('Y-m-d');
'birthdate' => [
'date_format:' . config('panel.date_format'),
'required',
'before:'.$before18Years,
],
file panel.php
<?php
return [
'date_format' => 'Y-m-d',
'time_format' => 'H:i:s',
'primary_language' => 'en',
];