Business Days and Holidays in ChatGPT
Working days and holidays. The MCP server is https://businessdays.openkrill.app/mcp. No key. The steps below are only for ChatGPT. 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 ChatGPT
ChatGPT does not read a local config file. A custom MCP server is added in the product, and only after developer mode is on. These steps were checked against OpenAI's plugin connect guide and the ChatGPT MCP guide on 2026-10-01. Developer mode can be hidden by a workspace policy, so a Team or Enterprise admin may have to allow it first.
- Open ChatGPT settings, then Security and login, and turn on Developer mode.
- Open ChatGPT plugins and select the plus button.
- Enter a name such as "Business Days and Holidays" and a one-line description of what you want it to answer.
- Under Connection, choose the public endpoint and paste
https://businessdays.openkrill.app/mcp. Include the/mcppath. Do not add a tunnel id: this server is already public. - Create the connection and review the tools ChatGPT lists. You should see
count_business_days,add_business_days,list_holidays. The feedback tools on the same server are optional and not required for the lookup. - Start a new conversation, add the connection from the tools menu, and ask: How many working days are there between 14 July and 18 August 2026 in Germany?
No API key and no OAuth client id are required. The server answers without a login. Calls are limited per network and per day, and a limit comes back as a tool error rather than a partial answer. If the tool list is stale after a server change, open the connection and select Refresh, then start a new conversation.
The ChatGPT desktop app, Codex CLI and IDE extension share a different config. In the desktop app, open Settings, then MCP servers, choose Add server, select Streamable HTTP, and paste the same URL. In ~/.codex/config.toml the equivalent is a table named mcp_servers.business-days with url = "https://businessdays.openkrill.app/mcp". ChatGPT on the web does not read that file. A published directory listing is also a different path: this page is the developer-mode connection, not a claim that Business Days and Holidays is already in the ChatGPT directory.
Treat the server as untrusted until you have read a few answers. A remote MCP server sees the arguments the model sends. Business Days and Holidays is read-only and documents what it sends onward on the privacy page.
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
- Business Days and Holidays in Claude
- Business Days and Holidays in Cursor
- Business Days and Holidays in Pi