compare_dates_post_draft

functions.php

function test_single_page() {
	$post_id = get_the_ID(); 
	$closing_date = get_post_meta($post_id,'closing_date',true);
	
	if($closing_date!='') {
		$today  = date("Y-m-d");
		$expire = date("Y-m-d",strtotime($closing_date)) ;
		$today_dt = new DateTime($today);
		$expire_dt = new DateTime($expire);
		if ($expire_dt < $today_dt) {  
			$post = array( 'ID' => $post_id, 'post_status' => 'Draft' );
			wp_update_post($post);
			// redirect 
			header('Location:'.get_site_url().'/jobs-overview/');
			exit();
			die();
		}
	}
}
add_action('wp_head', 'test_single_page');