Days

Calculate diff among sart and end

// Add Shortcode
function days_shortcode( $atts ) {

	// Attributes
	extract( shortcode_atts(
		array(
			'start' => 'now',
			'end' => 'now',
		), $atts )
	);

	// Code
         $init = new DateTime($start);
         $finit = new DateTime($end);
         $interval = $init -> diff($finit);
         return $interval -> format('%a');
}
add_shortcode( 'days', 'days_shortcode' );