I thought this might’ve worked; but throwing out an undefined variable…
$end_date_passed_check = DateTime::createFromFormat('Ymd', get_field('event_end_date'));
if ($end_date_passed_check < date('Ymd'))
{
$date_passed = 'date-passed';
}
<div class="each-programme-content <?php echo $date_passed; ?>"></div>