PlugRail Japanese Calendar — Claude Code MCP server
Works out Japanese holidays and business days from Cabinet Office data. Useful when deadlines or schedules in your project follow the Japanese calendar.
claude mcp add --transport http jp-calendar https://jp-calendar.plugrail.dev/mcpWhat PlugRail Japanese Calendar does
Four tools ship with the server: is_holiday, list_holidays, business_days_between and add_business_days. Your agent can ask whether a given date is a day off, pull the holiday list for a range, count business days between two dates, or shift a date forward by a number of business days.
Holiday data sits in Cloudflare D1, with Cloudflare KV handling the cache. The hosted endpoint is https://jp-calendar.plugrail.dev/mcp, and that is the quickest way in. Authentication, rate limiting and usage metering exist only on the hosted side, so a self-hosted copy does not inherit them.
Self-hosting means copying wrangler.example.jsonc to wrangler.jsonc under packages/servers/jp-calendar/, filling in your own Cloudflare resource IDs, creating the D1 database and KV namespace, then running pnpm --filter @plugrail/jp-calendar deploy. The project is independent of Japanese government bodies and carries no guarantee from them, so for anything legally binding check the primary source.
What it helps with
- check whether a date falls on a Japanese public holiday
- count business days between two dates, skipping days off
- push a deadline forward by a set number of business days
- list Japanese holidays across a date range
- keep a Japanese day off from being treated as a working day
Example prompts for the agent
- Check with jp-calendar whether May 3 is a holiday and tell me which one
- Count the business days between April 1 and June 30 on the Japanese calendar
- Add five business days to December 20 and give me the resulting date
How to install PlugRail Japanese Calendar
Platform CLI: remote server
claude mcp add --transport http jp-calendar https://jp-calendar.plugrail.dev/mcpPlatform CLI: remote server
codex mcp add plugrail-japanese-calendar --url https://jp-calendar.plugrail.dev/mcpConfig file
{
"mcpServers": {
"plugrail-japanese-calendar": {
"url": "https://jp-calendar.plugrail.dev/mcp"
}
}
}Config file
{
"servers": {
"plugrail-japanese-calendar": {
"type": "http",
"url": "https://jp-calendar.plugrail.dev/mcp"
}
}
}Platform CLI: remote server
gemini mcp add -t http plugrail-japanese-calendar https://jp-calendar.plugrail.dev/mcpStep by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about PlugRail Japanese Calendar
How do I install PlugRail Japanese Calendar in Claude Code?
Run claude mcp add --transport http jp-calendar https://jp-calendar.plugrail.dev/mcp.
What does PlugRail Japanese Calendar do?
It gives your agent Japanese calendar tools: holiday checks, holiday listings, business-day counts between dates, and adding business days to a date.
Can I host this MCP server myself?
Yes, the repository documents a Cloudflare self-hosting path: a D1 database, a KV namespace and a deploy through pnpm. Authentication, rate limiting and usage metering stay with the hosted service and do not carry over.
