Business Days & Workday Calc in Claude

Questions it answers

Count workdays, office days and PTO days between two dates, add business days for an SLA due date, or list bank holidays and school breaks. Ask "how many working days are there between 14 July and 18 August in Germany?", "what date is 37 business days after 11 August in England?", "is Monday a bank holiday in Bavaria?" or "what are the school holidays in Bavaria?".

Business Days and Workday Calculator does the date arithmetic exactly and reads each country's public holidays from Nager.Date, the UK's bank holidays from GOV.UK and school holidays from OpenHolidays, so the result does not depend on a guess about which days are holidays. People also call it OpenKrill Business Days. For trading and settlement days, pass calendars: NYSE (also Nasdaq), FED (the Federal Reserve, which Fedwire and DTC settlement follow), LSE, JPX or TARGET2, alone or joined with each other or with the country's public holidays, such as NYSE and FED for a US T+1 settlement date or TARGET2 and FED for euro-dollar spot. Other exchanges and banking calendars are not covered.

It says how it counted. A working day is any day that is not a weekend day (Saturday and Sunday unless you set another weekend) and not a public holiday of the country or region. When you add days, the start date is day 0 and is not counted; when you count a range, both ends are counted unless you say otherwise. Bank holidays that are not days off, optional days and half days such as Christmas Eve count as working days.

Add a region (for example DE-BY, GB-SCT or US-CA) to include that region's holidays. Without one, holidays that only some regions keep are not counted, and the answer lists them so you can see the difference.

It covers more than 200 countries and territories for public holidays and a smaller set, mostly in Europe, for school holidays. It moves up to 1000 business days at a time and reads up to eight calendar years in one question. Company closures, local observances and legal deadline rules are not included, so check the official calendar and the contract before relying on a date.

It stores nothing about you: answers are cached for up to 24 hours, and the only lasting record is a daily count of calls per tool.

Short questions this server answers, each with a direct answer: Count working days and business-day due dates.

What it can do

• Counts workdays, office days and PTO days between two dates for a country or region
• Adds or subtracts business days from a date, skipping weekends and public holidays
• Lists bank holidays and statutory public holidays of a country and year, by region
• Lists school holidays and school breaks where they are published
• States how days were counted, including the weekend and which holidays were applied

Tools

• count_business_days, Count working days, workdays and PTO. Use this when the user asks how many working days, business days, workdays, office days or PTO days there are between two dates, or for a statutory holiday count, for example "how many working days between 14 July and 18 August in Germany?" or "how many working days are left in December in Ontario?". Pass the country code, the start and end dates as YYYY-MM-DD, and a region when the user names a state or province. Both dates count by default (see includeStartDate and includeEndDate). Weekends are Saturday and Sunday unless weekendDays is set. Returns the business, calendar and weekend day counts, the holidays on working days, those only some regions keep, and the conventions used. For exchange trading days pass calendars, such as ["NYSE"], ["LSE"], ["JPX"] or ["TARGET2"]. Do not use it for hours, time zones, or date differences that do not exclude weekends and holidays.
• add_business_days, Calculate a business-day due date and SLA. Use this when the user asks what date is a number of working days, business days or workdays after or before a date, including an SLA due date or turnaround, for example "what date is 37 business days after 11 August in England?" or "5 working days before 20 December in the US". Pass the country code, the start date as YYYY-MM-DD, the number of days (negative for earlier) and a region when the user names one. The start date is day 0 and is not counted. Returns the resulting date and weekday, the holidays skipped, and the conventions used. At most 1000 business days. For a trade's settlement date (T+1, T+2) pass calendars, such as ["NYSE", "FED"], ["LSE"] or ["JPX"]. Do not use it for legal deadlines that follow their own court or contract rules, or for calendar-day offsets.
• list_holidays, List bank holidays and school breaks. Use this when the user asks which public holidays, bank holidays, statutory holidays or school breaks a country, state or province has in a year, for example "is Monday a bank holiday in Bavaria?", "public holidays in Vietnam in 2027" or "school holidays in Bavaria". Pass the country code and the year, a region when the user names one, and kind school for school holidays, which are published for a limited set of countries. Public holidays come back with the date, weekday, English and local name, whether they apply nationwide or in listed regions, and whether they are a day off. Do not use it for religious or cultural festival dates without a country, trading-day calendars, or company holidays.

Add Business Days & Workday Calc in Claude

Claude connects to a remote MCP server as a custom connector. The connection is made from Anthropic's cloud, not from your laptop, so the server must be on the public internet. Business Days & Workday Calc is. These steps were checked against Claude's custom-connector article (updated 2026-08-11) and the Claude Code MCP docs on 2026-10-01.

On a Pro or Max plan:

1. Open Customize, then Connectors.
2. Select the plus button, then Add custom connector.
3. Paste this URL. Leave Advanced settings empty: this server does not need an OAuth client id or secret.

   https://businessdays.openkrill.app/mcp

4. Select Add. The connector is yours. Anthropic has not reviewed it, and it is not a Directory listing.
5. In a conversation, open the plus button, then Connectors, and enable Business Days & Workday Calc. Ask: How many working days are there between 14 July and 18 August 2026 in Germany?

On Team and Enterprise, an Owner adds the connector first at Organization settings, then Connectors, then Add, then Custom, then Web, and pastes the same URL. Members then connect it from Customize. A Free plan can add one custom connector.

In Claude Code, add it from the project directory:

claude mcp add --transport http business-days https://businessdays.openkrill.app/mcp

That writes a local or user config. A JSON entry needs "type": "http" (or streamable-http) plus the url. An entry with a url and no type is skipped. Confirm with claude mcp get business-days. The tools you should see are count_business_days, add_business_days, list_holidays.

If Claude tries to fetch https://businessdays.openkrill.app/mcp from its code sandbox and reports HTTP 403, the block is Claude's sandbox network allowlist, not this server. The sandbox proxy answers 403 with x-deny-reason: host_not_allowed for every host outside the allowlist. Use the connector above instead: connector calls come from Anthropic's cloud and do not pass the sandbox proxy. To let the sandbox reach it as well, an Owner adds businessdays.openkrill.app under Settings, then Capabilities, then Additional allowed domains.

Enable the connector only in conversations that need it. Claude can call the tools while you work, including during research, so turn off any tool you do not want invoked. Business Days & Workday Calc does not write to your accounts. It still receives the arguments of each call. Read the privacy page before you paste anything that is not public.

If it does not work

A call checked on 2026-10-17

Germany 2026 is a published Nager.Date calendar, so the holiday names can be checked. The request below was posted to https://businessdays.openkrill.app/mcp as tools/call. HTTP 200. Source: the Business Days & Workday Calc server, read 2026-10-17.

{
  "method": "tools/call",
  "params": {
    "name": "list_holidays",
    "arguments": {
      "country": "DE",
      "year": 2026
    }
  }
}

• source. Public holidays: Nager.Date (date.nager.at). School holidays: OpenHolidays (openholidaysapi.org).
• year. 2026
• country. DE
• publicHolidays. 19 returned
• publicHolidays name. New Year's Day
• publicHolidays date. 2026-01-01

Repeat the call yourself if you need a newer reading. Cached answers expire. A rate limit is not a result: wait and try again. Nothing in the call is a ranking, a filing, or advice.

Using it in production

Nothing to install and nothing to run: no package, no Python or Node.js version and no environment variable. Business Days & Workday Calc runs on our servers, and your client only needs the URL https://businessdays.openkrill.app/mcp.

Use it in other apps

• Business Days & Workday Calc in ChatGPT
• Business Days & Workday Calc in Cursor
• Business Days & Workday Calc in VS Code
• Business Days & Workday Calc in Pi

Roles that use Business Days & Workday Calc

• Operations coordinator guide

Frequently asked questions

Words on this page

• MCP (Model Context Protocol) definition
• Streamable HTTP transport definition
• Tool primitive definition
• Rate limit policy definition

Source: plugin listing for business-days in this repository, and a live tools/call on 2026-10-17. As of 2026-10-17.