How to count business days, SLA due dates and regional public holidays without writing holiday tables

By OpenKrill. Published 2026-10-20. Every count, date and timing below comes from live calls to Business Days & Workday Calc (businessdays.openkrill.app), the US Office of Personnel Management holiday schedule and Nager.Date between 06:18 and 07:16 UTC on 2026-10-20.

The short answer

Open the Business Days and Workday Calculator or connect https://businessdays.openkrill.app/mcp to your AI assistant. Call count_business_days to count working days between two dates, add_business_days to find an SLA due date, or list_holidays to list public holidays and school breaks for a country and region. Every answer states its counting rules and names the exact holidays it skipped.

What our November 2026 US workday test showed

We asked: "How many business days are there in the US from 2026-11-02 to 2026-11-30, with both dates included?" In 1,106 ms, count_business_days returned 19 business days out of 29 calendar days, subtracting 8 weekend days and 2 federal holidays that fall on weekdays:

How Business Days & Workday Calc compared with rivals

We ran the same November 2026 US query against three common alternatives on 2026-10-20:

UK SLA turnarounds and German state holidays

Two more calls from today's test show how region codes and endpoint rules change the answer:

• 10 working days after 2026-12-18 in England (add_business_days). Passing country: "GB", region: "GB-ENG", startDate: "2026-12-18" and days: 10 returned 2027-01-06 (Wednesday). When adding business days, startDate is day 0 and is never counted. The 10-workday span covers 19 calendar days because it skips 3 weekends and 3 public holidays: Christmas Day (2026-12-25), the substitute St. Stephen's Day / Boxing Day bank holiday on Monday 2026-12-28, and New Year's Day (2027-01-01).
• 2026 public holidays in Bavaria vs nationwide Germany (list_holidays). Passing country: "DE", region: "DE-BY" and year: 2026 returned 12 statutory public holidays in Bavaria. Nine fall on weekdays: New Year's Day (2026-01-01), Epiphany (2026-01-06, Tuesday, kept only in DE-BW, DE-BY and DE-ST), Good Friday (2026-04-03), Easter Monday (2026-04-06), Labour Day (2026-05-01), Ascension Day (2026-05-14), Whit Monday (2026-05-25), Corpus Christi (2026-06-04, Thursday, kept in 6 states including DE-BY), and Christmas Day (2026-12-25). Three fall on weekends in 2026: German Unity Day (2026-10-03, Saturday), All Saints' Day (2026-11-01, Sunday), and St. Stephen's Day (2026-12-26, Saturday). A nationwide DE query without region: "DE-BY" leaves out Epiphany and Corpus Christi, changing a full-year workday count by 2 days.

Connect it to your AI client

Add https://businessdays.openkrill.app/mcp to your assistant, browse the pre-built 2026 country calendars on the Business Days calculator page, or follow the install steps for ChatGPT, Claude, Cursor and Pi. The agent job recipes are in business-days-jobs/SKILL.md.

Here is the JSON-RPC call for the US November 2026 workday count:

{"method":"tools/call","params":{"name":"count_business_days",
 "arguments":{"country":"US","startDate":"2026-11-02","endDate":"2026-11-30",
  "includeStartDate":true,"includeEndDate":true}}}

Common pitfalls in workday math

• Mixing up range counting and deadline addition. count_business_days includes both startDate and endDate by default, while add_business_days treats startDate as day 0 and starts counting on the next business day.
• Omitting the state or subdivision code. In countries like Germany (DE-BY), the UK (GB-ENG, GB-SCT) and the US, regional holidays are only subtracted when you pass region.
• Counting observance days or half days as statutory days off. Only holidays marked as Public in the calendar are subtracted; Christmas Eve and optional observances remain working days.
• Using a public-holiday calculator as a stock-market settlement calendar. Exchange trading calendars and legal court deadlines have their own rules and closures.

Frequently asked questions

How many business days are there between two dates in the US, excluding federal holidays?

Call count_business_days with country set to US and your startDate and endDate. For example, from 2026-11-02 to 2026-11-30 inclusive there are 19 business days out of 29 calendar days, skipping 8 weekend days plus Veterans Day (2026-11-11) and Thanksgiving Day (2026-11-26).

What date is 10 working days after a given date in the UK, counting bank holidays?

Call add_business_days with country GB, region GB-ENG (or GB-SCT / GB-NIR) and days 10. Starting on Friday 2026-12-18 in England, 10 working days lands on Wednesday 2027-01-06 after skipping Christmas Day, the 2026-12-28 Boxing Day substitute bank holiday and New Year's Day.

Which public holidays fall on weekdays in Germany in 2026, by state?

Call list_holidays with country DE, year 2026 and your state code such as DE-BY. In Bavaria, 9 of 12 public holidays fall on weekdays in 2026, including Epiphany (2026-01-06) and Corpus Christi (2026-06-04), while German Unity Day, All Saints' Day and 26 December fall on weekends.

Does Business Days & Workday Calc need an API key?

No. Both the web page and the MCP server at businessdays.openkrill.app/mcp are free and keyless, within 60 calls a minute per network.

Sources

• Workday counts, SLA turnarounds and holiday lists: Business Days & Workday Calc (https://businessdays.openkrill.app/mcp), read on 2026-10-20.
• US federal holiday schedule: U.S. Office of Personnel Management (OPM) 2026 federal holidays, read on 2026-10-20.
• Public holiday data source: Nager.Date public holiday API, read on 2026-10-20.
• School holiday data source: OpenHolidays API.
• Competitor package tested: commenthol/date-holidays version 3.37.0 on npm, tested on 2026-10-20.