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Can Claude count business days?

It often gets them wrong. Counting business days means walking a calendar day by day, skipping weekends and the federal holidays, including observed days when a holiday falls on a weekend, and language models are weak at that kind of exact date walk over weeks or months. Connect the free US Federal Holidays and Business Days server and Claude gets an exact count from the OPM rules, 1971 to 2100, plus due dates that roll past weekends and holidays.

Connect free, no token US federal holidays and business days MCP server

What Claude does alone, and what needs the server

Claude on its own

  • Lists the federal holidays and explains observed-day rules.
  • Counts short spans correctly most of the time.

With the US Federal Holidays and Business Days server

  • An exact business-day count between any two dates.
  • Adding N business days, and rolling an invoice due date.
  • The Federal Reserve banking calendar as a second option.

A real call to the live server

We sent this to the hosted server on 2026-11-03. The answer below is the server's own text, not a mock-up. Live values will differ when you ask.

You ask

How many business days are there from December 1, 2026 to January 15, 2027?

Tool call

count_business_days {"start_date":"2026-12-01","end_date":"2027-01-15"}

Server answer

There are 32 business days from 2026-12-01 to 2027-01-15 (start included, end included) on the federal calendar: 46 calendar days, 12 weekend days. Excluded weekday holidays: 2026-12-25 Christmas Day; 2027-01-01 New Year's Day.

Connect it in 1 minute

One URL, no token, no account. In Claude.ai or Claude Desktop open Settings, then Connectors, then Add custom connector, and paste the URL.

Connector URL

https://us-federal-holidays-business-days-mcp.lipmichal.workers.dev/mcp

Claude Code

claude mcp add --transport http us-federal-holidays-business-days https://us-federal-holidays-business-days-mcp.lipmichal.workers.dev/mcp

Cursor (~/.cursor/mcp.json)

{
  "mcpServers": {
    "us-federal-holidays-business-days": {
      "url": "https://us-federal-holidays-business-days-mcp.lipmichal.workers.dev/mcp"
    }
  }
}

VS Code (.vscode/mcp.json)

{
  "servers": {
    "us-federal-holidays-business-days": {
      "type": "http",
      "url": "https://us-federal-holidays-business-days-mcp.lipmichal.workers.dev/mcp"
    }
  }
}

All 5 tools, sources and more prompts: US federal holidays and business days MCP server · Create an invoice in Claude

Questions

Can Claude count business days?
It often gets them wrong. Counting business days means walking a calendar day by day, skipping weekends and the federal holidays, including observed days when a holiday falls on a weekend, and language models are weak at that kind of exact date walk over weeks or months. Connect the free US Federal Holidays and Business Days server and Claude gets an exact count from the OPM rules, 1971 to 2100, plus due dates that roll past weekends and holidays.
Does it know state holidays?
No. It uses the federal and Federal Reserve calendars. You can pass extra closed dates, such as a company shutdown, and they are skipped too.
What happens when a holiday falls on a Saturday?
Federal offices observe it on the Friday before. The Federal Reserve stays open that Friday, which is why the server has both calendars.
Is the server free?
Yes. The US Federal Holidays and Business Days server is free at its hosted URL with no token, key or account. The source is open on GitHub.

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