Why does the server reject EST, PST, and other three-letter codes?

Three-letter codes are ambiguous. 'CST' refers to both US Central (UTC-6) and China Standard Time (UTC+8). 'IST' is Indian, Israeli, and Irish. IANA names like `America/Chicago`, `Asia/Shanghai`, `Asia/Kolkata`, and `Europe/Dublin` are unambiguous and carry the full history of DST changes, which short codes do not.

Time MCP Server

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Time and timezone conversion utilities.

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Publisher

Anthropic

License

MIT

Transport

Local subprocess

Tools

What this server does

LLMs are unreliable narrators about 'now'. Training cutoff is months or years stale, prompt timestamps are often missing or wrong, and DST math is a known weak spot. A small Python server that wraps `zoneinfo` is more accurate than asking the model to compute it. The surface is two tools: `get_current_time(timezone)` returns the current time in an IANA timezone along with an `is_dst` flag; `convert_time(source_timezone, time, target_timezone)` converts an `HH:MM` 24-hour time between two zones and returns both sides plus a `time_difference` string like `+13.0h`. The server auto-detects your system timezone on launch. Pass `--local-timezone=America/New_York` if you are running headless or want a fixed default. Timezones must be IANA names: `Europe/London`, `Asia/Tokyo`, `America/Los_Angeles`. Three-letter codes (EST, PST) are not accepted because they are ambiguous: 'CST' is both US Central and China Standard Time, six hours apart. IANA names handle that plus historical DST changes correctly. Pair this with a calendar server for scheduling work, or with chat for the simple 'what time is it in Berlin?' question that the model would otherwise get wrong. Installs via `uvx mcp-server-time`, pip, or Docker.

Tools included

get_current_time
Return the current time in a given IANA timezone.
convert_time
Convert a time between two IANA timezones.

The authoritative list comes from the server's tools/list at runtime. This catalog entry may lag the upstream until the next ToolPiper release.

Install in ToolPiper

ToolPiper handles the JSON configuration. Click Install, fill in any required tokens, and the server is ready in your chat.

Don't have ToolPiper? We'll take you to the download.

Install in another client

Install in another MCP client (Claude Desktop, Cursor, Continue, Cline)

Add this to ~/Library/Application Support/Claude/claude_desktop_config.json.

{
  "mcpServers": {
    "time": {
      "command": "uvx",
      "args": [
        "mcp-server-time"
      ]
    }
  }
}

Example prompts

"What time is it in Tokyo right now?"
"When it's 4 PM in New York, what time is it in London?"
"Convert 9:30 AM Tokyo time to New York time."
"Is daylight saving in effect in Sydney today?"

Security notes

Local-only. No network calls, no env vars carrying credentials. The `--local-timezone` argument is the only knob, and the worst case for misconfiguration is an incorrect default zone, which is obvious the first time you ask for the current time. No reason to think about this server's posture beyond 'is it running.'

Common questions

Why does the server reject EST, PST, and other three-letter codes?: Three-letter codes are ambiguous. 'CST' refers to both US Central (UTC-6) and China Standard Time (UTC+8). 'IST' is Indian, Israeli, and Irish. IANA names like `America/Chicago`, `Asia/Shanghai`, `Asia/Kolkata`, and `Europe/Dublin` are unambiguous and carry the full history of DST changes, which short codes do not.