mcp-timezone

mcp-timezone

Work with clients in other countries without doing time zone arithmetic in your head. Ask "what time is it forMaria in Lisbon", "convert 3pm Warsaw to New York and Bangalore", or "find an hour next week that works for me,my client in New York and my designer in London" and get an answer you can act on: ranked meeting slots whereeveryone is inside their own working hours, the exact daily overlap, when the clocks change, how many businessdays a delivery date is, and a calendar file you can send. Saved contacts, working hours and nothing else liveas plain JSON on your own machine.

Built by theluckystrike.

Find a meeting time that works for everyone abroad, convert any time between cities, and write the invite -- zero setup, all local.

60-second install

npm publish for @theluckystrike/mcp-timezone is pending. Until then, the .mcpb one-click bundle or aclone+build is the working path -- both are verified below.

One-click (.mcpb): download timezone.mcpb from the latest release and double-click it in Claude Desktop:https://github.com/theluckystrike/mcp-servers/releases/latest

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "timezone": {
      "command": "npx",
      "args": ["-y", "@theluckystrike/mcp-timezone"]
    }
  }
}

Claude Code:

claude mcp add timezone -- npx -y @theluckystrike/mcp-timezone

Cursor (.cursor/mcp.json):

{
  "mcpServers": {
    "timezone": {
      "command": "npx",
      "args": ["-y", "@theluckystrike/mcp-timezone"]
    }
  }
}

The npx form above starts working the moment the package is published. Until then, use the .mcpb bundle above,or build from source with exactly these three commands:

git clone https://github.com/theluckystrike/mcp-servers.git && cd mcp-servers
npm install
npm run build -w packages/mcp-license -w servers/timezone

Then point your client's command at node with one arg: the absolute path to servers/timezone/dist/index.js.

To run in Pro mode set MCP_LICENSE_KEY in the same config block, or call license_activate once with your key.

Tools

Also exposed: the resource tz://contacts (saved contacts and their current local time) and the promptschedule_with (proposes times with saved contacts, then offers to write the invite).

What you can say

No tool names required.

Worked example

You: Find an hour next week for me in Warsaw, my client in New York and my designer in London.

  find_meeting_slots { participants: [{name:"Me",zone:"Warsaw"},{name:"Client",zone:"New York"},
                                     {name:"Designer",zone:"London"}], duration_minutes: 60, days: 5 }

Assistant: 15 slots fit all 3 participants. Best first:
  1. 2026-09-07T13:30:00.000Z  fairness 3.00h
     Me 15:30-16:30 | Client 09:30-10:30 | Designer 14:30-15:30

Three hours of fairness is not a flaw in the ranking, it is the truth about Warsaw and New York: with 09:00-17:00days on both sides the shared window is only 15:00-17:00 Warsaw, so somebody's meeting is always far from themiddle of their day. The score says so instead of hiding it. Widen one person's hours and the score improves.

You: Write the invite for that one, 45 minutes, and send it to [email protected].

  ics_create { title:"Kickoff with Acme", start:"2026-09-10 15:00", zone:"Warsaw",
               duration_minutes:45, attendees:[{name:"Maria Nowak", email:"[email protected]"}],
               organizer_email:"[email protected]" }

Assistant: Wrote /Users/you/.local/share/mcp-servers/timezone/meeting.ics
Kickoff with Acme: 2026-09-10 15:00 Thu (CEST, UTC+02:00) for 45 min
DTSTART 2026-09-10T13:00:00.000Z (UTC)

How the ranking works

find_meeting_slots scores every candidate by the worst participant's distance from 13:00 local, in hours,and sorts ascending. The worst, not the average, on purpose: a slot that is pleasant for two people and 07:00for the third must never outrank one that is 10:00 for everybody. A fairness of 0 would mean the meeting sitsat midday for all of them; anything under about 2 is comfortable.

A slot is only offered when the whole meeting -- start to end -- is inside every participant's working window,on their own local calendar day. Weekends in the first participant's zone are skipped. No slot ever startsbefore earliest_date -- if you pass a time with it, slots earlier that day are not proposed.

When nothing fits, the server says so, shows the windows, and then lists the closest times that areoutside somebody's hours, ranked by the total minutes outside, with each person's local time and theworking hours that would make each one fit. On the free tier a search longer than 5 days is shortened to5 days and the answer says so; it is never refused outright.

How places are resolved

City and country names resolve through a built-in table of 490 entries (300+ cities, every commonly usedcountry and US state shorthands). Every entry is verified againstIntl.supportedValuesOf("timeZone") at startup; an entry this Node build cannot resolve is dropped with aline on stderr rather than silently answering with the wrong zone.

• A country that spans several zones maps to its main business zone: United States -> America/New_York,Australia -> Australia/Sydney, Canada -> America/Toronto, Brazil -> America/Sao_Paulo, Russia -> Europe/Moscow,Mexico -> America/Mexico_City, Indonesia -> Asia/Jakarta. Name a city when you need a different one.
• IANA ids always work and always win: pass America/Denver and you get exactly that.
• UTC+2 style offsets resolve to the matching fixed zone (Etc/GMT-2 -- the Etc signs are inverted by theIANA database, not by this server).
• A fixed abbreviation is an offset, not a place. EST is Etc/GMT+5 (UTC-05:00) all year, PST isEtc/GMT+8, CET is Etc/GMT-1, JST is Etc/GMT-9. Mapping them to a DST-observing zone made ESTmean EDT (UTC-04:00) every summer, an hour wrong for half the year. Each answer carries a note naming theplace to pass instead ("New York", "Los Angeles", "Paris"). The region shorthands ET, CT, MT,PT still name places and keep their clock changes. IST is read as India (UTC+05:30, Asia/Kolkata,no daylight saving) and the note says so, because IST also names Irish and Israel time.
• An unknown name is never guessed. It comes back as an error with suggestions:unknown time zone or place: "Warsawa". Did you mean: warsaw (Europe/Warsaw)?

DST is not stored here at all. Every offset comes from the ICU data inside your Node build viaIntl.DateTimeFormat, so the rules stay current as Node updates instead of going stale in a bundled table.

Free vs Pro

Pro is $19 one-time, or $39 for every server in the bundle: Get Pro.Activation is offline: keys are Ed25519 signatures verified against a public key compiled into the package.

How it stores data

Contacts and the monthly .ics counter live in one JSON file:${XDG_DATA_HOME:-~/.local/share}/mcp-servers/timezone/data.json.

Every write happens under an advisory lock at .../timezone/.lock, held across the whole load-mutate-savecycle, so two clients sharing one data dir cannot discard each other's contacts. The save writes a temporaryfile and renames it into place, so a crash mid-write leaves either the old file or the new one.

If data.json is ever unreadable or not valid JSON, the server does not treat that as "no contacts yet".It moves the file aside byte-for-byte as data.json.corrupt-<timestamp>, writes a data.json.corrupt marker,and every later call fails with data file is corrupt; moved to ...; nothing was written until you restore agood copy and delete the marker.

Dates, times and honest caveats

• A time with no offset is wall-clock time in from_zone, not UTC. 2026-09-10 15:00 withfrom_zone: "Warsaw" is 15:00 in Warsaw. A trailing Z or an explicit +05:30 is honoured exactly andfrom_zone is then only used for display.
• A calendar date is validated, not normalised. 2026-02-30 is refused with the reason (February 2026has 28 days) everywhere a date is read: convert_time, overlap, business_days, ics_create and theholiday list. Nothing is ever rolled forward into March.
• A wall time inside a spring-forward gap does not exist, and is refused. 02:30 on 2026-03-29 inWarsaw comes back as an error naming both valid neighbours (2026-03-29 01:30 and 2026-03-29 03:30).Pass gap:"forward" to take the time after the jump or gap:"backward" for the one before it; the answerthen says which it used. Guessing silently is how a meeting moves an hour once a year.
• Ambiguous times in the autumn fold return the FIRST occurrence and say so: 02:30 on 2026-10-25 inWarsaw is 00:30Z, the CEST reading. Pass fold:"second" for 01:30Z, the CET one. Both answers namethe abbreviation and offset they used.
• .ics attendees are calendar addresses. An attendee with an email becomesATTENDEE;CN="Name";RSVP=TRUE:mailto:addr, with CN written as a quoted RFC 5545 parameter value. A namewith no email is listed in DESCRIPTION instead of being written as an unroutable address. Any CR, LF orcontrol character in any field is refused, not escaped away: it is what a content-line injection lookslike. organizer_email writes the ORGANIZER line; without it no ORGANIZER is written and the answersays so, because replies then have nowhere to go.
• .ics files carry UTC times (DTSTART:20260910T130000Z) and no VTIMEZONE block. That is deliberate:a hand-written VTIMEZONE with stale DST rules is the classic way an invite lands an hour off.
• Working hours are the only calendar this server has. It does not know about your existing meetings,public holidays (pass them to business_days yourself) or anyone's lunch. business_days says so inits own answer when no holiday list is passed, so a "22 business days" figure is never mistaken for apublic-holiday-adjusted one.
• Argument sizes are capped, so a runaway caller cannot turn one call into a hang or a huge reply:place and date strings 100 characters, event titles 200, descriptions 5000, up to 50 zones,100 participants, 100 attendees, 400 holidays, days <= 366, duration_minutes <= 1440, and abusiness_days range of at most 3700 days (longer ranges are refused, never silently truncated).
• out_path is written where you name it. ics_create resolves a relative path against theprocess working directory and does not confine it to the data directory; an unwritable path returnsa clean EACCES and consumes none of the free monthly quota.
• Weekend skipping uses the first participant's zone and the Saturday/Sunday convention. A Friday-Saturdayweekend is not modelled; set work_start/work_end or read the dates.

Troubleshooting

• npx hangs or fails to find the package: npm publish is pending. Use the .mcpb bundle or theclone-and-build path above.
• A city is not recognised: the error lists suggestions. Any IANA id always works, soAmerica/Argentina/Cordoba is available even when the city name is not in the table.
• Node version: requires Node >= 18. Check with node -v. Older builds ship older DST rules.
• Nothing shows up / silent failures: this server writes to stderr only, never stdout. In Claude Desktopcheck Settings -> Developer -> the server's log; in Claude Code run with --mcp-debug.
• A Pro key isn't recognized: run license_status, and confirm MCP_LICENSE_KEY is set in the process theclient launches, not just your shell.

Privacy

All data stays local: contacts live in ${XDG_DATA_HOME:-~/.local/share}/mcp-servers/timezone/data.json.The server makes no network requests, has no telemetry and needs no account. Time zone data comes from theICU database already inside Node.

Pairs with

• mcp-time-tracker -- track the hours you spend on those clients and report them.
• mcp-invoice -- turn the tracked hours into a numbered PDF invoice for the client abroad.
• office-suite -- several servers behind one install, one config entry.

FAQ

Does it handle daylight saving?Yes, and it does not store any DST rules of its own. Every offset is read from the ICU data in your Nodebuild, so Warsaw and New York being 5 hours apart (not 6) between 8 and 29 March 2026 falls out correctly.

Why is my best slot still awkward?Because a real overlap can be two hours wide. The fairness score reports the worst person's distance fromtheir midday so you can see the cost and decide who absorbs it.

Can I use half-hour zones?Yes. India (+05:30), Nepal (+05:45), Adelaide (+09:30) and Chatham are handled like any other zone; the slotgrid is 30 minutes, so a half-hour zone produces :00 and :30 local starts.

Does it read my calendar?No. It knows only the working hours you give it. It writes .ics files; it never reads or connects to acalendar service.

Does it need an internet connection?No. There are no network calls anywhere, including license activation.

License

MIT