Like Vince Carter said, overnight ! = next day. It has always meant next business day, and that is more UPS/FedEx than it is Defy or the pharmacy.
https://www.ups.com/us/en/shipping/services/domestic/overnight-delivery.page
I am not familiar in shipping lingo. How is one to assume overnight = next day = next business day? It would be less confusing if worded 'next business day' for the laymen as mysef.