A deadline expressed in business hours cannot be calculated as a simple difference between two timestamps. From Friday at 16:00 to Monday at 10:00, many calendar hours pass but only a few fall inside normal office hours.
GuideBest practicesIntermediate
How to calculate business hours between two dates and times
Understand the difference between business days, business hours and working time, then calculate useful time inside opening hours.
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Business day, business hour and worked hour
A business day is a day included in the working calendar, typically Monday to Friday in Bethemesh’s generic calculation. A business hour is time inside a defined opening window, such as 09:00–17:00. A worked hour is time actually worked by a person, possibly after subtracting breaks.
Use the business hours calculator for available opening time and the work hours calculator for an individual’s net working time.
Example across several days
For a period from Thursday 15:00 to Monday 11:00 with opening hours 09:00–17:00, Monday to Friday: Thursday contributes 2 hours, Friday 8, Saturday and Sunday 0, and Monday 2. Total: 12 business hours.
Counting business days alone is not enough when start and end times matter. Business-hour calculations are useful for support windows, processing deadlines, service availability and operational periods crossing a weekend.
Holidays and exceptions
A generic Monday-to-Friday calculation does not automatically represent every real business calendar. Public holidays, exceptional closures and organization-specific non-working days may need separate handling. Bethemesh deliberately separates technical calculation from legal or contractual rules.
A reliable manual method is to identify included days, remove non-business days, clip each remaining day to opening hours and add the durations. The calculator automates those steps locally in your browser.