72 hours.
You have many misinformed answers. It's unbelievable!
A business day depends on the company you are talking about.
I'll repeat, "A business day depends on the company you are referencing."
If they are open on Saturday, that IS a business day. If they are open on a legal holiday, that IS a workday.
The minute they are open to accept deliveries, that starts a 24 hour clock even if they are only open for 4 hours.
It has NOTHING to do with when a delivery company is open. For instance, here in the USA the post office delivers on Saturday in most areas, but not all. So if the company is open on Saturday but the post office doesn't deliver on that day, it is still considered a 24 hour business day and deducted from the 72 hour total.
Likewise there are delivery companies that deliver on a Sunday for express shipments, but a company that is not open on Sunday does not consider that a 24 hour business day, although they may have a drop box available to accept deliveries on Sunday.
So 3 business days are 72 hours long.