How long is a business day
Jsm36 is correct.
A business day is about 8 1/2 to 9 hours depending on your work schedule.
As long as it needs to be to get the work done, but general business hours are 8-5. You can usually get someone on the phone during those hours.
If you're talking shipping, as in ' you should receive your order in 7-10 business days', they're basically talking mon- fri. Regardless of hours in the work day.