# Focus Room World Clock

> Local times, UTC offsets and daylight saving in several cities, plus the best meeting hours. Shows one moment on the clocks of up to twelve time zones — local date and time, weekday, UTC offset, daylight saving and the day difference — as a table and as analogue clock faces, then plans a meeting: for each hour of the day it lists how many places are inside their working hours, so you can see at a glance when everyone is at work. The Focus Room app shows the same clocks as a live world-clock strip.

Part of usefulweb.app (https://usefulweb.app/). Part of [Focus Room](https://focusroom.usefulweb.app/) (ownerApp: focusroom). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://focusroomworldclock.usefulweb.app/ (interactive tool at https://focusroomworldclock.usefulweb.app/tool)
- JSON API: POST https://focusroomworldclock.usefulweb.app/api/v1/calculate with a JSON object of inputs (schema: https://focusroomworldclock.usefulweb.app/api/v1/tool)
- OpenAPI: https://focusroomworldclock.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://focusroomworldclock.usefulweb.app/mcp - tool `focusroom_world_clock`

## Inputs
- zones (list): Time zones - One IANA name per line; the first one is the reference for day differences and the meeting planner.
- at (datetime): Moment (optional) - Empty = now (rounded down to the minute).
- atZone (text): Time zone of that moment - IANA time-zone name such as Europe/Berlin, America/New_York, Asia/Kolkata or UTC.
- workStart (integer): Working hours start
- workEnd (integer): Working hours end

## Method
- Local times, offsets and weekdays come from the IANA time-zone database through the platform’s Intl implementation. Daylight saving time = the zone’s offset at that moment is above the smaller of its January and July offsets that year.
- Day difference = local date of the zone minus the local date of the first zone.
- Meeting planner: the day of the moment in the first zone is split into its 24 local hours; an hour counts for a place when that whole hour lies inside the working hours on a Monday to Friday there. Best hours are those with the highest count.
- Clock faces are drawn with rotated lines only (hour hand 30° per hour plus 0.5° per minute, minute hand 6° per minute), so every device draws the same picture.