Agent Tools / MCP install guides / Business Days and Holidays in Claude

Business Days and Holidays in Claude

Working days and holidays. The MCP server is https://businessdays.openkrill.app/mcp. No key. The steps below are only for Claude. A call to list_holidays was checked against that server on 2026-10-01.

What this server answers

Count working days between two dates, add business days to a date, or list a country's public holidays. 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 Holidays does the date arithmetic exactly and reads each country's public holidays from Nager.Date, with school holidays from OpenHolidays, so the result does not depend on a guess about which days are holidays.

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.

What it can do

Counts the working days between two dates for a country or region
Adds or subtracts business days from a date, skipping weekends and public holidays
Lists the public holidays of a country and year, by region
Lists school holidays for countries and regions where they are published
States how days were counted, including the weekend and which holidays were applied

Tools

count_business_days, Count business days between dates. Use this when the user asks how many working days, business days or workdays there are between two dates, for example "how many working days between 14 July and 18 August in Germany?", "how many working days are left in December in Ontario?" or "does 16 days of leave cover 5 to 31 December?". 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 are counted by default (includeStartDate and includeEndDate change that). Weekends are Saturday and Sunday unless weekendDays is set. Returns the number of business days, calendar days and weekend days, the public holidays that fell on working days, the holidays only some regions keep, and the conventions used. Do not use it for hours, time zones, or date differences that do not exclude weekends and holidays.
add_business_days, Add business days to a date. Use this when the user asks what date is a number of working or business days after or before a date, for example "what date is 37 business days after 11 August in England?", "when is payment due 30 business days from invoice date 3 March in Germany?" 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. Do not use it for legal deadlines that follow their own court or contract rules, or for calendar-day offsets.
list_holidays, List public and school holidays. Use this when the user asks which public holidays, bank holidays or school holidays 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 and Holidays 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 and Holidays 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:

Open Customize, then Connectors.
Select the plus button, then Add custom connector.
Paste https://businessdays.openkrill.app/mcp. Leave Advanced settings empty: this server does not need an OAuth client id or secret.
Select Add. The connector is yours. Anthropic has not reviewed it, and it is not a Directory listing.
In a conversation, open the plus button, then Connectors, and enable Business Days and Holidays. 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.

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 and Holidays 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.

A call checked on 2026-10-01

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 and Holidays server, read 2026-10-01.

{
  "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.

Same server, other clients

Roles that use Business Days and Holidays

Operations coordinator guide

Terms used on this page

Source: plugin listing for business-days in this repository, and a live tools/call on 2026-10-01. As of 2026-10-01.