Hi,
"product sale start" and "product sale end" are options for the indication on where the product would be available and when the product will stop to be sell.
These options would "block" the access of the product. It means that, after the sale end, the product wouldn't be available.
You can display theses values but, outsides theses dates, it would not be possible to see the product.
To display them, you have to edit the "product show_default" view and
if(!empty($this->element->product_sale_start))
echo date("m/d/Y", $this->element->product_sale_start);
Regards,