Magento – How to check final price or special price is valid or expire on magento 1.9

For me, this fixed it: Promotions > Catalog Price Rule > YOUR RULE > Actions > Enable Discount to Subproducts > YES >set the discount exactly the same as you did above it.

You can do this by below code:

    if($product->getPrice()>$product->getFinalPrice()):
    // product in sales
    endif;

If want only basic of Special price,Then you can try the below:

$specialprice = $product->getSpecialPrice();
$specialPriceFromDate = $product->getSpecialFromDate();
$specialPriceToDate = $product->getSpecialToDate();
$today =  time();

if ($specialprice && ($product->getPrice()>$product->getFinalPrice())):
        if($today >= strtotime( $specialPriceFromDate) && $today <= strtotime($specialPriceToDate) || 
    $today >= strtotime( $specialPriceFromDate) && is_null($specialPriceToDate)):
   //product in sales
    endif; 
endif;