Chrono

A zero-dependency date & time MCP server. One file, pure Python standard library — no mcp package, no pip install, no virtualenv. AI agents are notoriously bad at knowing today's date, doing timezone math, and remembering DST rules; this server gives them seven precise, tested tools for exactly that.

{"mcpServers": {"chrono": {"command": "python3", "args": ["/absolute/path/to/chrono_mcp.py"]}}}

Why

• AI models don't know what time it is. Training data ends months before you ask; "today" is a guess. This server gives the real clock.
• Timezone math is where agents hallucinate. "Is Shanghai 12 or 13 hours ahead of New York right now?" depends on when "now" is, because of DST. All conversions here are DST-aware via the IANA database.
• Zero dependencies, by design. No supply chain, no version conflicts, nothing to audit. If you have Python 3.9+ you already have everything. The MCP protocol layer (JSON-RPC 2.0 over stdio) is implemented in the same file.

Tools

Tool	What it does	Example
get_current_time	Real current date/time in any IANA zone (or city alias)	{"timezone": "tokyo"}
convert_time	Wall-clock conversion across zones with day-rollover detection	09:00 Shanghai → 21:00 New York (previous day)
time_offset	Live UTC-offset difference between two zones (DST-aware)	Shanghai → New York = -12h00m in September
parse_natural_time	Free-form phrase → precise ISO timestamp	"next tuesday 3pm", "3 days ago", "sep 10 3pm"
add_duration	Signed duration arithmetic, incl. business days	"+3 hours", "-2h30m", "3 business days"
meeting_windows	Common meeting slots across timezones within local business hours	Shanghai + London → 16:00 / 09:00
format_time	strftime formatting with optional zone conversion	%A, %B %d %Y %I:%M %p

City aliases work anywhere a timezone is accepted: tokyo, beijing, new york, san francisco, london, dubai, utc, and ~40 more.

Install

Any MCP client (Claude Desktop, Cursor, Windsurf, …)

Clone and point your client at the file:

{
  "mcpServers": {
    "chrono": {
      "command": "python3",
      "args": ["/absolute/path/to/chrono-mcp/chrono_mcp.py"]
    }
  }
}

Claude Desktop: claude mcp add chrono -- python3 /absolute/path/to/chrono-mcp/chrono_mcp.py

Requirements

• Python 3.9+ with the zoneinfo module (standard on 3.9+; on Windows also install tzdata from PyPI if zone lookups fail).

Example phrases parse_natural_time understands

Phrase	Result (Asia/Shanghai)
next tuesday 3pm	the coming Tuesday, 15:00 local
tomorrow 09:00	tomorrow, 09:00 local
tonight	today, 20:00 local
in 2 hours / 3 days ago	relative to real current time
friday 9:00	the coming Friday
last friday	the most recent Friday
2026-09-10 14:30	exact datetime
sep 10 3pm / september 10, 2026 2pm	month-name dates

Example: meeting_windows

meeting_windows(timezones=["Asia/Shanghai", "Europe/London"], date="2026-09-02")
→ windows: [{ start_utc: 08:00, local_start: {Shanghai: 16:00, London: 09:00} }, …]

For a genuinely impossible pair (Shanghai + New York within 9–18 local), the server returns a clear No common window message with suggestions instead of guessing.

Run the tests

python3 -m unittest discover -s tests

47 tests, covering every tool plus end-to-end JSON-RPC over a real subprocess (initialize → tools/list → tools/call, error recovery, notification handling).

Protocol notes

Implements the stdio transport of the Model Context Protocol: newline-delimited JSON-RPC 2.0 with initialize, notifications/initialized, ping, tools/list, tools/call. Tool errors are returned as isError: true results (the server never crashes on bad input); unknown methods return -32601.

License

MIT