bizdays

Verified business-day math for AI agents — holidays + per-country weekends, not guesses.

LLMs are good at "what's 5 + 3" and bad at "what date is 5 business days after Dec 22nd in the UK." They forget holidays, miscount, and assume every country's weekend is Saturday/Sunday. bizdays gives an agent the deterministic answer, with the weekend rule and the holidays it skipped shown in the response.

It's both an MCP server (so any agent can call it live) and a typed TypeScript library (so you can import the same functions in your own code).

Part of Qiniso — verified, trustworthy data tools for AI agents.

Why it exists

Two things break naive business-day calculations, and bizdays fixes both:

1. Weekends are not Sat/Sun everywhere. Saudi Arabia, Egypt, Israel and Qatar use Friday/Saturday; Iran's is Friday; India's is Sunday; the UAE moved to Saturday/Sunday in 2022. bizdays resolves the weekend from Unicode CLDR per country, with a curated override layer for places CLDR gets wrong (e.g. Bangladesh is Fri/Sat, Nepal is Saturday-only).

2. "Holiday" must mean a real day off. Off-the-shelf holiday data often counts observances like Valentine's Day, Tax Day or Christmas Eve as holidays. Those are not days off. bizdays counts only public holidays, so your deadlines don't silently drift.

Related MCP server: Nager MCP UI MCP Server

Install

npm install @qinisolabs/bizdays

Use as an MCP server

Hosted (one paste, no install): Settings → Connectors → Add custom connector and paste:

https://bizdays.qinisolabs.workers.dev/mcp

Local (stdio): run it yourself with npx -y @qinisolabs/bizdays, or wire it into an MCP client:

{
  "mcpServers": {
    "bizdays": { "command": "npx", "args": ["-y", "@qinisolabs/bizdays"] }
  }
}

Tools exposed:

Use as a library

import { addBusinessDays, countBusinessDays, isBusinessDay } from "@qinisolabs/bizdays";

addBusinessDays("2025-12-22", 5, "GB").result;        // "2025-12-31" (skips Christmas + Boxing Day)
countBusinessDays("2025-12-01", "2025-12-31", "US");  // { businessDays: 22, ... } (excludes Christmas)
isBusinessDay("2025-06-13", "SA").isBusinessDay;       // false — Friday is weekend in Saudi Arabia
isBusinessDay("2025-02-14", "US").isBusinessDay;       // true — Valentine's Day is not a public holiday

Every function returns a rich result object: the answer, the weekday, exactly which weekends and named holidays were skipped, the weekend rule and its source, and a confidence flag.

Data & coverage

• Holidays: public holidays for 206 countries (and subdivisions), via date-holidays, filtered to type: "public".

• Weekends: Unicode CLDR via the runtime Intl API, plus a curated data/weekend-overrides.json correction layer maintained by Qiniso.

• Confidence: a Tier-1 list of ~65 countries has its weekend rule manually verified and (where a calendar exists) holiday parity-tested; results for those are flagged verified. Everything else still works but is flagged unverified so the agent knows.

• No holiday calendar for a country? (e.g. Qatar, Kuwait, Oman) — bizdays still applies the correct weekend and tells you, via holidaysApplied: false, that holidays were not applied. Pass extraHolidays to supply your own.

Dates are plain YYYY-MM-DD strings, handled in UTC — no timezone surprises.

Notes

• The start date is never counted by add_business_days; the result is always a business day.

• count_business_days includes both endpoints by default (set inclusive: false to drop the start).

• Need company shutdown days or regional holidays? Pass them as extraHolidays (an array of YYYY-MM-DD).

License

Apache-2.0. Bundled holiday data is from date-holidays (ISC AND CC-BY-3.0); see NOTICE.