Magento_Catalog/templates/product/price/final_price.phtml

//THIS CODE WILL HELP US WRITE TEXT UNDER THE PRICE SUCH AS BOGO, ETC
  $objectManager = MagentoFrameworkAppObjectManager::getInstance();
  $_productdata = $objectManager->get('MagentoCatalogModelProduct')->load($productId);
  unset($promo_text);
  $promo_text = $_productdata->getData('promo_text');
  $promo_text_start_date = $_productdata->getData('promo_text_start_date');
  $promo_text_end_date = $_productdata->getData('promo_text_end_date');
  $todays_datefor_promo_text = date('Y-m-d h:i:s');

  if($promo_text !='')
  {

      if($todays_datefor_promo_text >= "$promo_text_start_date 00:00:00" && $todays_datefor_promo_text <= "$promo_text_end_date 11:59:59")
       {
          echo "<p class='bogotextcolor'>$promo_text</p>";
       }
  }