A free, no-auth MCP tool that does date arithmetic across bank and exchange calendars — and shows its working.
Ask any model to add business days across a holiday and it counts calendar days, guesses the holiday set, and hands you a plausible date with no indication it is wrong. There is no error, no hedge, no “I’m not sure”. It is the worst shape a mistake can take.
The single nastiest case: 4 July 2026 falls on a Saturday. The Federal Reserve does not observe it — Friday 3 July is a normal Fed business day. The NYSE does close that Friday. Same date, opposite answers, one day of drift on a settlement or a notice period.
| Thursday 2 July 2026, +1 business day | Answer |
|---|---|
US_FED — Federal Reserve | Friday 3 July |
US_NYSE — exchange | Monday 6 July |
Claude Desktop — claude_desktop_config.json. Cursor and Cline take the same shape.
{
"mcpServers": {
"buddylists": {
"command": "npx",
"args": ["-y", "mcp-remote", "https://www.buddylists.dev/api/mcp"]
}
}
}
Then ask, in plain language: “Our contract gives 10 business days’ notice from 2 April 2026 under both US and UK banking calendars — what’s the deadline?”
curl "https://www.buddylists.dev/api/business-days?start_date=2026-04-02\ &add_business_days=10&calendars=US_FED,UK_BANK"
Returns 2026-04-20, and tells you it skipped Good Friday and Easter Monday to get there. No key, no signup, nothing stored.
US_FED | US Federal Reserve bank holidays |
US_NYSE | New York Stock Exchange trading days |
UK_BANK | UK bank holidays (England & Wales) |
TARGET2 | TARGET2 / ECB euro settlement |
Ask for several and they intersect: a day counts only if every market is open.
Every calendar is dumpable, so you can audit this against the official source instead of taking our word for it:
curl "https://www.buddylists.dev/api/business-days?list=US_FED&year=2026"
Ten holidays in 2026, not eleven. If that surprises you, re-read the first section.
Dates are UTC calendar dates with no local-time conversion. Four calendars, not forty. Early exchange closes (half-days) are not modelled — the tool tells you whether a market is open, not for how long. Holiday rules are computed, not fetched, so a one-off royal or national holiday announced mid-year will not appear until the repo is updated.