How to get next day date of a specific day

Use the parameters of the shortcode with lowercase: [recurring_event short=”Wed” full=”wednesday”]

Try to follow the next code:

// NAV: Custom Code
function wpcoder_recurring_event_att( $atts ){
$date="";
$default = array(
    'short' => 'Sun',
    'full' => 'sunday'
);
$eventday = shortcode_atts($default, $atts);
date_default_timezone_set('US/Eastern');
if(date('D') == $eventday["short"]) { 
   echo date('F d, Y');
}
else {
  // Create a new DateTime object
  $date = new DateTime();

 // Modify the date it contains
  $date->modify($eventday['full']);
    
    $date->modify('+1 day');

  //output
  echo $date->format('F d, Y');
 }
}
// register shortcode
add_shortcode('recurring_event', 'wpcoder_recurring_event_att');

You can add the code in the file ‘functions.php’ or add using the free plugin WP Coder via the page Global PHP