When does a business day start and end?

For date-calculation purposes, a business day is a full calendar day (midnight to midnight). The calculator does not use clock times — it works in whole calendar days. In practice, business hours vary by country and industry, typically running from 9:00 AM to 5:00 PM local time. If you need hour-level precision, this calculator gives you the calendar date; apply your local business hours to that date.