The Holiday Calendar MCP server,
connected in one click.
U.S. federal holidays with observed dates and business-day math. Example from an open-source kit. Connect the official Holiday Calendar MCP server to Claude, ChatGPT, or Cursor through gate — one gateway URL, no config files, security-checked.
Free to start · No credit card · No hosting needed
Add Holiday Calendar to your AI in one minute
Pick your client. Copy, paste, done — or let gate handle sign-ins and policies for you.
claude mcp add --transport http holiday-calendar https://starter.modernmustardseed.com/holidaysRun in your terminal, then restart Claude Code.
Holiday Calendar · https://starter.modernmustardseed.com/holidays
What your AI can do with Holiday Calendar
Real prompts you can type the moment it's connected — no setup, no docs to read.
“Use “list_federal_holidays”: List the eleven U.S. federal holidays for one calendar year (2021 through 2100): each holiday's name, its actual date and weekday, the date.”
“Use “next_federal_holidays”: Find the next one to eleven U.S. federal holidays observed on or after a date, with each one's observed date and how many calendar days away.”
“Use “check_business_day”: Check whether a date is a U.S. business day (a weekday that is not an observed federal holiday). Returns the weekday, the holiday observed t.”
“Use “add_business_days”: Move a number of U.S. business days forward or backward from a date, skipping weekends and observed federal holidays, for due dates, deliver.”
How secure is the Holiday Calendar MCP server?
Every server in the gate directory has to pass the same four checks before your AI can touch it. Here's how Holiday Calendar holds up.
Official endpoint
Operated by Holiday Calendar (modernmustardseed.com) at its documented MCP endpoint — not a third-party mirror or community re-host.
No sign-in needed
This server only exposes public data — no account and no credentials are involved when you connect.
Scanned before it goes live
gate checks every tool for prompt injection, hidden instructions, data-exfiltration hints, and over-broad permissions before the server is available through your gateway.
Watched for drift
If Holiday Calendar adds or changes tools later, gate re-scans and alerts you — before your AI acts on the change.
Connected in three steps
Connect your gate
Add one gateway URL to Claude, ChatGPT, or any MCP client. One-time setup, about two minutes.
Pick Holiday Calendar
Choose Holiday Calendar in the gate directory. No sign-in needed.
Use it anywhere
Holiday Calendar's tools are live in every AI client you've connected — with rules and logging built in.
Free to start · No credit card · No hosting needed
The actual tools Holiday Calendar exposes
Fetched live from the official endpoint and re-checked daily by gate — not marketing copy.
list_federal_holidays — List the eleven U.S. federal holidays for one calendar year (2021 through 2100): each holiday's name, its actual date and weekday, the date
next_federal_holidays — Find the next one to eleven U.S. federal holidays observed on or after a date, with each one's observed date and how many calendar days away
check_business_day — Check whether a date is a U.S. business day (a weekday that is not an observed federal holiday). Returns the weekday, the holiday observed t
add_business_days — Move a number of U.S. business days forward or backward from a date, skipping weekends and observed federal holidays, for due dates, deliver
count_business_days — Count the U.S. business days between two dates, both dates included, leaving out weekends and observed federal holidays. Returns the busines
Who runs the Holiday Calendar MCP server?
The Holiday Calendar MCP server at a glance
https://starter.modernmustardseed.com/holidaysQuestions, answered
Is there an official Holiday Calendar MCP server?
Yes — Holiday Calendar operates its own remote MCP server at starter.modernmustardseed.com. gate connects you to that official endpoint and adds security scanning, per-tool access rules, and an activity log on top.
How do I connect Holiday Calendar to Claude or ChatGPT?
Add gate's gateway URL to your AI client once, then pick Holiday Calendar in the directory. No account or sign-in is needed. From then on, Holiday Calendar's tools are available in every client you've connected to gate.
Do I need to host anything?
No. Holiday Calendar runs the server, and gate is fully managed. You just connect one URL — there's nothing to install, deploy, or maintain.
Is the Holiday Calendar MCP server safe to connect?
It's the vendor's official endpoint, and gate scans its tools for prompt injection and hidden instructions before it goes live, re-checks it whenever it changes, and lets you allow, block, or require approval for every single tool.
Is it free?
Yes — you can get started with gate for free and connect Holiday Calendar in minutes. No credit card required.
Connect more than just Holiday Calendar
Every server below works through the same gateway URL — connect once, add tools anytime.
Squarespace DomainsDesignView →Set up Holiday Calendar in: Claude · Claude Code · ChatGPT · Cursor · VS Code
Give your AI Holiday Calendar — safely.
One URL. All MCPs. Full control. Free to start.
Get started free