Counting rules
Include start end date business days between
Include start end date business days between is the inclusion choice that controls edge days in the business day counter. It stops off-by-one slips when you switch between exclude both, include start, include end, and include both. This guide explains the four modes, shows worked examples, and helps you pick the right option in the calculator before you share a total.
Published: December 28, 2025 · Updated: December 28, 2025 · By FinToolSuite Editorial
Disclaimer
- Educational purposes only; not legal or financial advice.
- Examples are illustrative and simplified.
- Results depend on your inputs and assumptions and are not guaranteed.
- Read the Privacy Policy; do not share personal data.
Quick answer: include start end date business days between
- Exclude both removes start and end dates from the total.
- Include start or end keeps that edge if it is a business day.
- Include both adds two edge days when they are not weekends or excluded holidays.
The four inclusion modes explained
Exclude both
Removes start and end, common for “between” wording.
Include start
Counts day one if it is not filtered by weekend or holiday rules.
Include end
Keeps the end date when it is a valid business day.
Include both
Adds up to two days; use when wording says “inclusive”.
Worked examples
| Mode | Range (Mon to Fri, no holidays) | Total |
|---|---|---|
| Exclude both | Mon 01 to Fri 05 | 3 business days |
| Include start | Mon 01 to Fri 05 | 4 business days |
| Include end | Mon 01 to Fri 05 | 4 business days |
| Include both | Mon 01 to Fri 05 | 5 business days |
Common mistakes
- Mixing calendar days with business day totals.
- Changing inclusion mode mid-project without noting it.
- Forgetting holidays that sit on the start or end date.
- Leaving the wrong weekend pattern selected.
- Assuming “within” means the same as “inclusive”.
- Not sharing the rule set when handing off calculations.
How to set it in the tool
- Open the business day calculator.
- Select your start and end dates.
- Set weekend pattern and choose holiday presets or custom dates.
- Pick the inclusion mode: exclude both, include start, include end, or include both.
- Review the business day counter and share the assumptions.
Try it now: business day counter.
FAQ
What does include start end date business days between mean?
It controls whether start and end dates are counted as business days when they are kept.
What are the four inclusion modes?
Exclude both, include start, include end, include both.
Why do off by one errors happen?
Using the wrong mode or switching it mid-way changes the total by one or two days.
Do holidays affect inclusion modes?
Yes. A start or end date on a holiday will be excluded if holidays are removed.
Can I use custom weekends?
Yes. Set Friday–Saturday or Sunday–Thursday patterns before counting.
Why did my count change after toggling holidays?
Removing or adding holidays changes which days are kept, including edges.
Is this guaranteed?
No. Results depend on your inputs and assumptions and are not guaranteed.
Is this legal or financial advice?
No. This is educational. Confirm rules with your advisor.
Calculate business days now
Set the inclusion mode, weekend pattern, and holidays, then run the business day counter and share the assumptions.