Delete Me

function auto_delete_mails() {
  var label = GmailApp.getUserLabelByName("Delete Me");
  if(label == null){
    GmailApp.createLabel('Delete Me');
  }
  else{
    var delayDays = 2 // Enter # of days before messages are moved to trash
    var maxDate = new Date();
    maxDate.setDate(maxDate.getDate()-delayDays);
    var threads = label.getThreads();
    for (var i = 0; i < threads.length; i++) {
      if (threads[i].getLastMessageDate()<maxDate){
        threads[i].moveToTrash();
      }
    }
  }
}