Business Days & Workday Calc in ChatGPT

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 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.

1. Open ChatGPT settings, then Security and login, and turn on Developer mode.
2. Open ChatGPT plugins and select the plus button.
3. Enter a name such as "Business Days & Workday Calc" and a one-line description of what you want it to answer.
4. Under Connection, choose the public endpoint and paste this URL. Include the /mcp path. Do not add a tunnel id: this server is already public.

   https://businessdays.openkrill.app/mcp

5. 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.
6. 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 & Workday Calc 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 & Workday Calc is read-only and documents what it sends onward on the privacy page.

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 Claude
• 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.