[I'm writing this in English because I've searched the internet for a solution to my question and was unable to find anything useful.]
So, for the past two months I had a project for an online shop. I accepted the project as a challenge, because my experience with Magento was null. I was looking for a way to mark products as new, and later on I had to mark them as a promotion (here I wanted to use percentage). After a lot of googling I stumbled upon this little trick. But having to make a whole new attribute, meaning the client would have to do something more just for that made me feel uncomfortable. But I accepted it as a solution. A few days ago I had to do the percentage bit. So I proceeded to making the custom attribute, in which the client would have to input the % the price was off. That’s when I discovered I can easily use ANY attribute to my advantage.
The first thing I did was to redo the marking of new products. I was able to get the “from date”, the “to date” and I could determine the “now”. Here’s the code:
<?php
$nfd = strtotime($_product->getNewsFromDate()); //I like working with seconds so I'm transforming everything to epoch
$ntd = strtotime($_product->getNewsToDate()); // Same as above
$now = strtotime('now');
$price = $_product->getSpecialPrice();
$discounted = $_product->getPrice();
$discount = round(($price/$discounted)*100); //This is the formula for percentage
if ($nfd < $now && $now < $ntd) { // This verifies if "now" is between the "from" and "to" dates..
?>
<!--<div class="discount"><?php echo $discount . '%'; ?></div>-->
<div class="new-product">produs nou</div> // .. and if it is, we do whatever we want with it.
<?php } ?>
It has to be used in template/catalog/product/list.phtml.The above code also takes out the percentage of discount. Yes, it’s damn simple, but I was unable to find anything useful, just some Magento extensions, all having a price over 50$. I really hope it helps, and if you find this useful please share to other beginners 
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