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How to Calculate Business Days Between Two Dates
Formula
Counting business days (also called working days) between two dates is essential for project planning, payroll processing, and deadline management. Unlike calendar days, business days exclude Saturdays and Sundays, giving you an accurate count of actual workdays. This calculator uses the day-of-year and day-of-week to compute the number of Monday-through-Friday working days in any span.
The calculation works by first determining the total calendar days in the range, then computing how many complete weeks fit within that span (each contributing 5 business days). The remaining partial-week days are evaluated against the starting day of the week to determine how many of those fall on weekdays versus weekends. This approach gives you an accurate business day count without needing to iterate through every individual date.
Common use cases:
- Project deadline and milestone planning
- Payroll period calculations
- Shipping and delivery time estimates
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